• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.653-658
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• 2016

Poly(ether-block-amide)(PEBAX$_{(R)}$) resin is a thermoplastic elastomer combining linear chains of hard-rigid polyamide block interspaced soft-flexible polyether block. It was believed that the hard polyamide block provides the mechanical strength and permselectivity, whereas gas transport occurs primarily through the soft polyether block. The objective of this work was to investigate the gas permeation properties of carbon dioxide and methane for PEBAX$^{(R)}$-1657 membrane, and compare with those obtained for other grade of pure PEBAX$^{(R)}$, PEBAX$^{(R)}$-2533 and PEBAX$^{(R)}$ based hybrid membranes. The hybrid membranes based PEBAX$^{(R)}$ were obtained by a sol-gel process using GPTMS ((3-glycidoxypropyl) trimethoxysilane) as the only inorganic precursor. Molecular structure and morphology of membrane were analyzed by $^{29}Si$-NMR, DSC and SEM. PEBAX$_{(R)}$-2533 membrane exhibited higher gas permeability coefficients than PEBAX$^{(R)}$-1657 membrane. This was explained by the increase of chain mobility. In contrast, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$-1657 membrane was higher than PEBAX$^{(R)}$-2533 membrane. It was explained by the decrease of diffusion selectivity caused by increase of chain mobility. For PEBAX$^{(R)}$/GPTMS hybrid membrane, gas permeability coefficients were decreased with reaction time. Gas permeability coefficient of $CH_4$ was more significantly decreased than $CO_2$. It can be explained by the reduction of chain mobility caused by the sol-gel process, and strong affinity of PEO segment with $CO_2$. Comparing with pure PEBAX$^{(R)}$-1657 membrane, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$/GPTMS hybrid membrane has decreased to 4.5%, and gas permeability coefficient of $CO_2$ has increased 3.5 times.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.523-533
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• 2022

Several prediction model of penetration rate (PR) of tunnel boring machines (TBMs) have been focused on applying to design stage. In construction stage, however, the expected PR and its trends are changed during tunneling owing to TBM excavation skills and the gap between the investigated and actual geological conditions. Monitoring the PR during tunneling is crucial to rescheduling the excavation plan in real-time. This study proposes a sequential prediction method applicable in the construction stage. Geological and TBM operating data are collected from Gunpo cable tunnel in Korea, and preprocessed through normalization and augmentation. The results show that the sequential prediction for 1 ring unit prediction distance (UPD) is R²≥0.79; whereas, a one-step prediction is R²≤0.30. In modeling algorithm, a gradient boosted regression tree (GBRT) outperformed a least square-based linear regression in sequential prediction method. For practical use, a simple equation between the R² and UPD is proposed. When UPD increases R² decreases exponentially; In particular, UPD at R²=0.60 is calculated as 28 rings using the equation. Such a time interval will provide enough time for decision-making. Evidently, the UPD can be adjusted depending on other project and the R² value targeted by an operator. Therefore, a calculation process for the equation between the R² and UPD is addressed.

• International Journal of Quality Innovation
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• v.6 no.2
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• pp.105-115
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• 2005

In recent years, high-speed recording CD-R has already become the mainstream of CD-R market. Therefore, to promote the efficiency of recording CD-R is of significant importance. This study uses Taguchi's parameter design to improve the yield rate for the process of CD-R substrate. We have found 13 three-level controllable factors from the fishbone diagram, repeated 10 times the experiment with the L27(313) orthogonal array, and measured seven quality characteristics. We employ four general methods to find the optimal parameter conditions individually. Then, we perform the confirmation experiment and compare the results. Finally, we obtain the optimal parameter conditions. According to the analysis of benefits, the optimal parameter conditions can reduce the quality loss of CD-R substrate to about 21%. In the future, the results can be extended to other research of DVD-R substrate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.163-164
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• 2013

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.149-155
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• 2015

This paper proposes 5-MS/s 10-bit digital-to-analog converter(DAC) with the improved linearity. The proposed DAC consists of a 10-bit R-2R-based DAC, an output buffer using a differential voltage amplifier with rail-to-rail input range, and a band-gap reference circuit for the bias voltage. The linearity of the 10-bit R-2R DAC is improved as the resistor of 2R is implemented by including the turn-on resistance of an inverter for a switch. The output voltage range of the DAC is determined to be $2/3{\times}VDD$ from an rail-to-rail output voltage range of the R-2R DAC using a differential voltage amplifier in the output buffer. The proposed DAC is implemented using a 1-poly 8-metal 130nm CMOS process with 1.2-V supply. The measured dynamic performance of the implemented DAC are the ENOB of 9.4 bit, SNDR of 58 dB, and SFDR of 63 dBc. The measured DNL and INL are less than +/-0.35 LSB. The area and power consumption of DAC are $642.9{\times}366.6{\mu}m^2$ and 2.95 mW, respectively.

• Journal of Convergence for Information Technology
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• v.9 no.1
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• pp.12-18
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• 2019

The purpose of this study is to analyze the effects of government's R&D investment outcome on the IT industry. The analysis of R&D investment outcome developed emphasizing qualitative outcome more than quantitative outcome. However, it is still leaning on technological outcome-centered methods, having relatively little interest in inputs that actually determine the outcome. Thus, this study intends to focus on the qualitative attributes of input resources. The results of the empirical analysis can be summarized as follows. In raising technological outcome and commercialization outcome of R&D investment, more funds per researcher and numbers of researchers and a longer development period had positive effects. However, a higher ratio of doctors had positive effects only on technological outcome (papers and patents), It is believed that leading to commercialization outcome needed a long period, but the period of task development was only an average of two years. On the contrary, collaboration had negative effects on technological process, which indicates that collaboration between two organizations having conflicting interests would lead to negative effects on the outcome. The results show that the qualitative attributes of input resources have significant effects on R&D investment outcome, and imply that it is necessary to emphasize the qualitative attributes from the input stage to promote government's R&D investment outcome in the future.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.18-21
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• 2007

Highly textured MgO template by ion-beam-assisted deposition(IBAD) was successfully fabricated using a continuous reel-to-reel(R2R) mode. To enlarge the deposition area, the previous IBAD system was modified into the system with 14-pass and five heating zone. Every processing step was carried out using this multi-turn IBAD system. The overall process consists of R2R electropolishing of a hastelloy C276 tape, deposition of $Al_2O_3$ diffusion barrier, $Y_2O_3$ seed layer, IBAD-MgO and homoepi-MgO layer. The IBAD-MgO templates were fabricated using the IBAD system with 216 cm-length deposition zone and 32 cm diameter ion source. The texture of MgO films developed during the IBAD process was monitored by in-situ reflection high energy electron diffraction(RHEED) to optimize the IBAD process. Recently, 100 m long IBAD-MgO tape with in-plane texture of $\Delta{\phi}<10^{\circ}$ was successfully fabricated using the modified IBAD system. In this report, the detailed deposition condition of getting a long length IBAD-MgO template with a good epitaxy is described.

• Journal of the Korea Society for Simulation
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• v.2 no.1
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• pp.46-54
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• 1993

Analytic and simulation models for prioritized token ring are presented in this paper. Its protocol is based on prioritized token ring with reservation (R-PTR). Since the protocol of the R-PTR is simple and the performance of the R-PTR is not inferior to that of the IEEE-PTR under almost all traffic load environments, we use the R-PTR as our token ring model. By using the properties of Markovian process, the expressions for average throughput and average packet transmission delay are derived. The results obtained from the analytic model are compared with that of the discrete event simulation model.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.2
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• pp.89-94
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• 2018

Due to industrial advancement and environmental concerns, there is a demand for light-weight material parts with high-performance characteristics. In order to meet this demand, various studies have been conducted on developing high-performance castings to achieve composite features by coating only specific parts that require high performance, with dissimilar joining, rather than coating the entire material part. This study analyzed the possibility of forming a local composite layer on an aluminum alloy through evaporation pattern casting, and the effects of parameters on the aluminum alloy.

• Journal of the Korean Data and Information Science Society
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• v.26 no.2
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• pp.323-334
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• 2015

he current VaR model based on the J.P. Morgan's RiskMetrics structurally can not reflect the future economic situation. In this study, we propose a One-factor model resulting from the Wiener stochastic process decomposed into a systematic risk factor and an idiosyncratic risk factor. Therefore, we are able to perform a preemptive risk management by means of reflecting the predicted common risk factors in the model. Stocks in the portfolio are satisfied with the independence to each other because the common factors are fixed by the predicted value. Therefore, we can easily determine the investment in each stock to minimize the variance of the portfolio. In addition, the portfolio VaR is decomposed into the sum of the individual VaR. So we can effectively implement the constitution of the portfolio to meet the target maximum losses.