• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.1-6
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• 2017

More addition of calcium carbonate in printing paper allows savings of the wood fibers and the drying energy. Pre-flocculation of GCC (ground calcium carbonate) using functional polymers was known as the best available technology to make high loaded paper until now, and it allowed less reduction of the paper essential properties such as tensile strength and smoothness at higher GCC content. However, pre-flocculated GCC became unstable in size under the continued agitation in the mill. Therefore, pre-flocculation method was modified in such a way that the in-situ calcium carbonate was formed between the GCC particles of the pre-flocculated GCC, and the resultant became more stable in size, which we named as HCC (hybrid calcium carbonate). HCC turned out to make high tensile strength and smoothness as much as the pre-flocculated GCC and gave much better size stability against stirring. Furthermore, HCC gave high bulk that pre-flocculation could not make.

• Geomechanics and Engineering
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• v.38 no.3
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• pp.319-334
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• 2024

The current theories on the interaction between surrounding rock and support in deep-buried tunnels do not consider the form of pre-reinforcement support or the flexibility of primary support, leading to a discrepancy between theoretical solutions and practical applications. To address this gap, a comprehensive mechanical model of the tunnel with pre-reinforced rock was established in this study. The equations for internal stress, displacement, and the radius of the plastic zone in the surrounding rock were derived. By understanding the interaction mechanism between flexible support and surrounding rock, the three-dimensional construction analysis solution of the tunnel could be corrected. The validity of the proposed model was verified through numerical simulations. The results indicate that the reduction of pre-deformation significantly influences the final support pressure. The pre-reinforcement support zone primarily inhibits pre-deformation, thereby reducing the support pressure. The support pressure mainly affects the accelerated and uniform movement stage of the surrounding rock. The generation of support pressure is linked to the deformation of the surrounding rock during the accelerated movement stage. Furthermore, the strength of the pre-reinforcement zone of the surrounding rock and the strength of the shotcrete have opposite effects on the support pressure. The parameters of the pre-reinforcement zones and support materials can be optimized to achieve a balance between surrounding rock deformation, support pressure, cost, and safety. Overall, this study provides valuable insights for predicting the deformation of surrounding rock and support pressure during the dynamic construction of deep-buried weak rock tunnels. These findings can guide engineers in improving the construction process, ensuring better safety and cost-effectiveness.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.3
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• pp.8-18
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• 2002

• Journal of Korean Society of Environmental Engineers
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• v.33 no.9
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• pp.656-661
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• 2011

The performance of a domestic ceramic membrane with pore size of $0.1{\mu}m$ was evaluated to produce drinking water. A pilot-scale ceramic membrane filtration plant with a capacity of $1m^3/d$ was operated at the filtration flux of $3.0m^3/m^2{\cdot}d$ to investigate the effect of both backwash interval and pre-ozonation on TMP (trans-membrane pressure) increasing rate. The TMP increased with increasing the backwash interval. However, the application of pre-ozonation reduced the TMP increasing rate remarkably. When 1 mg/L of ozone was dosed with contact time of 5 min, TMP increasing rate at the backwash interval of 1 hr was reduced by 30%. This result indicated that pre-ozonation was very effective in reducing membrane fouling. There was almost no change in TMP increasing rate when the ozone contact time was maintained in the range of 5 to 15 min. Increasing ozone concentration up to 3 mg/L showed beneficial effect on TMP increasing rate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.7
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• pp.531-536
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• 2012

We herein present results of flat and uniform polymer-blended small molecular semiconductor thin films. Which were produced for organic thin film transistors (OTFTs), using a simple pre-metered horizontal dipping process. The organic semiconducting thin films were composed of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) composite blended with a polymer binder of poly(${\alpha}$-methylstyrene) (PaMS). We show that the pre-metered horizontal-dip-coating(H-dip-coating) process allowed the critical control of the thickness of the blended TIPS-PEN:PaMs thin film. The fabricated OTFTs using the TIPS-PEN:PaMs films exhibited maximum field-effect mobility of $0.22\;cm^2\;V^{-1}\;s^{-1}$. These results demonstrated that H-dip-coated TIPS-PEN:PaMS films show considerable promise for the production of reliable, reproducible, and high-performance OTFTs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.305-314
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• 2001

A modified model is proposed for calculation of transitional boundary layer flows. In order to develop the eddy viscosity model for the problem, the flow is divided into three regions; namely, pre-transition region, transition region and fully turbulent region. The pre-transition eddy-viscosity is formulated by extending the mixing length concept. In the transition region, the eddy-viscosity model employs two length scales, i.e., pre-transition length scale and turbulent length scale pertaining to the regions upstream and the downstream, respectively, and a universal model of stream-wise intermittency variation is used as a function bridging the pre-transition region and the fully turbulent region. The proposed model is applied to calculate three benchmark cases of the transitional boundary layer flows with different free-stream turbulent intensity (1%∼6%) under zero-pressure gradient. It was found that the profiles of mean velocity and turbulent intensity, local maximum of velocity fluctuations, their locations as well as the stream-wise variation of integral properties such as skin friction, shape factor and maximum velocity fluctuations are very satisfactorily predicted throughout the flow regions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.78-85
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• 2019

The effect of various lithium sources such as LiCl, LiOH, and Li-metal on the microstructure and electrochemical properties of granulated $SiO_x$ powders were investigated. Various lithium sources were metallurgically added for a passive pre-lithiation of $SiO_x$ to improve its low initial coulombic efficiency. In spite of using the same amount of Li in various sources, as well as the same process conditions, different lithium silicates were obtained. Moreover, irreversible phases were formed without reduction of $SiO_x$, which might be from additional oxygen incorporation during the process. Accordingly, there were no noticeable electrochemical enhancements. Nevertheless, the $Li_4SiO_4$ phase changes the initial electrochemical reaction, and consequently the relationship between the microstructure and electrochemical properties of metallurgically pre-lithiated $SiO_x$ could provide a guideline for the optimization of the performance of lithium ion batteries.

• Journal of Broadcast Engineering
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• v.11 no.2 s.31
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• pp.191-199
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• 2006

This paper presents an efficient pre echo control scheme for MPEG Audio coders based on the psychoacoustic model II (PAM-II). Pre echo control is the final step for the calculation of masking threshold in the PAM II. It is to minimize the spread of quantization error over the processing frame. In the conventional encoders, pre echo is reduced by restricting the estimated masking threshold not to exceed the one obtained in the previous frame. The conventional method performs pre echo control not only for short blocks but also for long blocks, which lowers the masking threshold in long blocks and, in turn, increases the quantization noise level of corresponding blocks. This paper proposes an efficient pre echo control process. The test result shows a mean enhancement of more than 0.4 especially for complex signals on the ITU R 5 point audio impairment scale.

• Journal of KIISE:Databases
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• v.41 no.4
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• pp.209-216
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• 2014

Various characteristics of social network contents such as real-time, people relationship and big data can help to improve personalized recommender systems. Among them, 'people relationship' is a key factor of recommendation, so many personalized recommender systems utilizing it have been proposed. However, existing researches can not reflect personal tendency and are unable to provide precise recommendations in various domains, because they do not consider intimacy among people. In this paper, to solve these problems, we propose PReAmacy, a Personalized Recommendation Algorithm, considering intimacy among users and various characteristics of social network contents. Our experimental results indicate that not only the precision of PReAmacy is higher than that of existing algorithms, but intimacy is of great importance in PReAmacy.

• Proceedings of the KIEE Conference
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• 1976.08a
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• pp.59-63
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• 1976