Modeling and economic analysis of CO<Subscript>2</Subscript> separation process with hollow fiber membrane modules

The main purpose of the study was to develop a model using ASPEN and Excel simulation method to establish optimum CO₂ separation process utilizing hollow fiber membrane modules to treat exhaust gas from LNG combustion. During the simulation, optimum conditions of each CO₂ separation scenario were determined while operating parameters of CO₂ separation process were varied. The characteristics of hollow fibers membrane were assigned as 60 GPU of permeability and 25 of selectivity for the simulation. The simulation results illustrated that 4 stage connection of membrane module is required in order to achieve over 99% of CO₂ purity and 90% of recovery rate. The resulted optimum design and operation parameters throughout the simulation were also correlated with the experimental data from the actual CO₂ separation facility which has a capacity of 1,000 Nm³/day located in the Korea Research Institute of Chemical Technology. Throughout the simulation, the operating parameters of minimum energy consumption were evaluated. Economic analysis of pilot scale of CO₂ separation plant was done with the comparison of energy cost of CO₂ recovery and equipment cost of the plant based on the simulation model. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Physical and electroresponsive characteristics of the intercalated styrene‐acrylonitrile copolymer/clay nanocomposite under applied electric fields

Styrene‐acrylonitrile copolymer (SAN)/clay nanocomposites were synthesized through an emulsion copolymerization of styrene and acrylonitrile in the presence of sodium montmorillonite, and their physical properties and electroresponsiveness under an applied electric field were characterized. Thermogravimetric analysis (TGA) showed that the thermal stability of the synthesized polymer was sustained. X‐ray diffraction (XRD) analysis confirmed the insertion of SAN into the interlayers of clay, whose separation consequently increased, as compared to those of the pristine clay. Transmission electron microscopy (TEM) was used to observe the suspended state of clay. Dry‐base electrorheological (ER) fluids were prepared by mixing intercalated SAN nanocomposite particles into silicone oil. Typical ER behavior, i.e., enhancement of shear and yield stresses in the presence of an applied electric field, was observed using a rotational rheometer equipped with a high‐voltage generator. A universal yield stress scaling equation was also found to fit our experimental data well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 821–827, 2003     

Fabrication of high-efficiency anatase TiO2 photocatalysts using electrospinning with ultra-violet treatment

In metal oxide nanofiber fabrication using the electrospinning method, heat treatment is performed at temperatures of 500°C or higher for crystallization and polymer desorption. Therefore, it is difficult to fabricate low-temperature phase metal oxides that crystallize at low temperatures. TiO₂, a representative metal oxide often used as photocatalysts, is known to have higher photocatalytic activity in the low-temperature phase (anatase structure) than in the high-temperature phase (rutile structure). Studies on the fabrication of TiO₂ anatase nanofibers using conventional electrospinning have reported disadvantages such as the partial expression of rutile structures and low crystallinity. This study developed an anatase TiO₂ nanofiber as a high-efficiency catalyst based on the electrospinning method and a residual organic matter cleaning method that employs ultra-violet (UV) light. We fabricated nanofibers using the electrospinning method and implemented TiO₂ nanofibers with the anatase structure through heat treatment at 260°C. Residual organics remaining after heat treatment of the fabricated crystalized TiO₂ nanofibers were removed by exposing them to UV light, thereby improving photocatalytic efficiency. The photocatalytic efficiency of the fabricated TiO₂ nanofibers was confirmed through a methylene blue (MB) decomposition experiment under visible light irradiation. The photocatalytic efficiency (time taken for the concentration of the MB solution to reach 50%) of the UV-treated TiO₂ nanofibers was approximately six times higher than of P25 and the heat-treated nanofibers.     

Comparison of liquid-phase and methanol-swelling crosslinking processes of polyimide dense membrane for CO2/CH4 separation

To overcome the plasticization effect in polyimide membranes, many researchers have proposed crosslinking method. This can reduce an inter-segmental mobility by tightening and rigidifying the polymer chains. However, it is difficult to modify the whole polymer chains throughout the membrane because the reaction can be hindered by the diffusion rate of the crosslinker. In particular, it is hard for bulky crosslinker to penetrate a dense membrane with a small d-spacing. This study investigated the effect of crosslinking a dense Matrimid membrane with p-phenylenediamine (p-PDA) via two different crosslinking methods (i.e., methanol-swelling crosslinking process [M-SCP] and liquid-phase crosslinking process [L-PCP]). Most of the crosslinking reaction in M-SCP occurs on the membrane surface due to difficulty in penetration of the bulky p-PDA into the Matrimid dense membrane. In contrast, the L-PCP allows uniform crosslinking across the membrane. The membranes crosslinked using L-PCP showed excellent chemical resistance. Furthermore, the plasticization phenomenon was not observed in the membranes crosslinked using L-PCP with p-PDA more than 15%. Meanwhile, the membrane crosslinked using M-SCP exhibited poor plasticization and chemical resistance properties. These results showed that the L-PCP method can be more effective for the crosslinking of dense membrane to deliver both high plasticization and chemical resistance.     

Preparation and characterization of thermoresponsive poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide) hydrogel materials for smart windows

In this study, a series of thermoresponsive cross-linked copolymer poly [N-isopropylacrylamide(NIPAm)-co-N-isopropylmethacrylamide(NIPMAm)] (P-M series samples: P-M-0, 10, 20, 30, 40, where numbers are co-monomer contents) hydrogels were prepared by free radical polymerization using the main monomer N-isopropylacrylamide (NIPAm), co-monomer N-isopropylmethacrylamide (NIPMAm), cross-linking agent N, N-methylenebisacrylamide, initiator (ammonium persulfate)/catalyst, and solvent water. In addition, a series of samples [P-G series samples: P-G-0, 10, 20, 30, 40, where numbers are co-solvent glycerol content) were prepared using P-M-40 as components and water/co-solvent glycerol as a mixed solvent. The effects of co-monomer NIPMAm and co-solvent glycerol contents on the lower critical solution temperature (LCST)/freezing temperature and light transmittance as function of temperature of the prepared copolymer gels were investigated. The resulting thermoresponsive polymer gels had LCSTs in the range of 17.9 to 38.7°C and freezing points in the range of 6.3 to −38.5°C. These gels are suitable materials for smart windows that are responsive to various environmental conditions.     

A study of tailored blank welding between mild steel sheet and zn-coated steel sheet by CO2 laser beam

Research was conducted on tailored blank welding between mild steel sheet and Zn-coated steel sheet using CO₂ laser beam. The materials used in this study were low carbon steel sheets with a thickness of 1.2 mm and Zn-coated steel sheet with the same thickness and 6.3 μm Zn coating. Experiments were conducted by applying the Taguchi method to obtain optimum conditions for the application of this tailored blank laser welding method in practical manufacturing processes. Optical microscopy, XRD, SEM and TEM analysis were performed to observe the microstructures and to determine the structures of welded zone. In addition, mechanical properties were measured by the microhardness test, tensile test and Erichsen test to evaluate the formability of the welded specimen. There was no trapped Zn in the fusion zone, and the phases of this region consisted of polygonal ferrite, quasi-polygonal ferrite, banitic ferrite and martensite. The elongation value of welded specimen was more than 80% of the value in substrate metal, and the LDH value was more than 90% of the value in substrate metal.     

Object tracking based on an online learning network with total error rate minimization

This paper presents a visual object tracking system which is tolerant to external imaging factors such as illumination, scale, rotation, occlusion and background changes. Specifically, an integration of an online version of total-error-rate minimization based projection network with an observation model of particle filter is proposed to effectively distinguish between the target object and the background. A re-weighting technique is proposed to stabilize the sampling of particle filter for stochastic propagation. For self-adaptation, an automatic updating scheme and extraction of training samples are proposed to adjust to system changes online. Our qualitative and quantitative experiments on 16 public video sequences show convincing performances in terms of tracking accuracy and computational efficiency over competing state-of-the-art algorithms.     

A timing controller embedded driver IC with 3.24‐Gbps eDP interface for chip‐on‐glass TFT‐LCD applications

This paper presents a timing controller embedded driver (TED) IC with 3.24‐Gbps embedded display port (eDP), which is implemented using a 45‐nm high‐voltage CMOS process for the chip‐on‐glass (COG) TFT‐LCD applications. The proposed TED‐IC employs the input offset calibration scheme, the zero‐adjustable equalizer, and the phase locked loop‐based bang‐bang clock and data recovery to enhance the maximum data rate. Also, the proposed TED‐IC provides efficient power management by supporting advanced link power management feature of eDP standard v1.4. Additionally, the smart charge sharing is proposed to reduce the dynamic power consumption of output buffers. Measured result demonstrates the maximum data rate of 3.24 Gbps from a 1.1 V supply voltage with a 7.9‐inch QXGA 60‐Hz COG‐LCD prototype panel and 44% power saving from the display system.     

Nonparametric approach for uncertainty-based multidisciplinary design optimization considering limited data

Uncertainty-based multidisciplinary design optimization (UMDO) has been widely acknowledged as an advanced methodology to address competing objectives and reliable constraints of complex systems by coupling relationship of disciplines involved in the system. UMDO process consists of three parts. Two parts are to define the system with uncertainty and to formulate the design optimization problem. The third part is to quantitatively analyze the uncertainty of the system output considering the uncertainty propagation in the multidiscipline analysis. One of the major issues in the UMDO research is that the uncertainty propagation makes uncertainty analysis difficult in the complex system. The conventional methods are based on the parametric approach could possibly cause the error when the parametric approach has ill-estimated distribution because data is often insufficient or limited. Therefore, it is required to develop a nonparametric approach to directly use data. In this work, the nonparametric approach for uncertainty-based multidisciplinary design optimization considering limited data is proposed. To handle limited data, three processes are also adopted. To verify the performance of the proposed method, mathematical and engineering examples are illustrated.