• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.609-617
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• 2017

Lignocellulosic biomass is a renewable resource for production of biofuels and biochemicals. Furfural (FF) is an important platform chemical catalytically derived from the hemicellulose fraction of biomass. Tetrahydrofurfuryl alcohol (THFA) is a FF derivative and can be used as an eco-friendly solvent with thermal and chemical stability. Despite large numbers of experimental studies for catalytic conversion of FF to THFA, few research have conducted on the economic feasibility for large-scale THFA production from FF. At the stage of assessment of the potential for commercialization of conversion technology, a large-scale process study is required to identify technological bottleneck and to obtain information for solving scale-up problems. In this study, process simulation and technoeconomic evaluation for catalytic conversion of FF to THFA are performed, as the following three steps: integrated process design, heat integration, and economic evaluation. First, a large-scale process including conversion and separation processes is designed based on experimental results. When the FF processing rate is 255 tonnes per day, the FF-to-THFA yields are 63.2~67.9 mol%. After heat integration, the heating requirements are reduced by 14.4~16.4%. Finally, we analyze the cost drivers and calculate minimum selling price of THFA by economic evaluation. The minimum selling price of THFA for the developed process are $2,120~2,340 per tonne, which are close to the current THFA market price.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.417-417
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• 2016

Global environmental deterioration has become more serious year by year and thus scientific interests in the renewable energy as environmental technology and replacement of fossil fuels have grown exponentially. Photoelectrochemical (PEC) cell consisting of semiconductor photoelectrodes that can harvest light and use this energy directly to split water, also known as photoelectrolysis or solar water splitting, is a promising renewable energy technology to produce hydrogen for uses in the future hydrogen economy. A major advantage of PEC systems is that they involve relatively simple processes steps as compared to many other H2 production systems. Until now, a number of materials including TiO2, WO3, Fe2O3, and BiVO4 were exploited as the photoelectrode. However, the PEC performance of these single absorber materials is limited due to their large charge recombinations in bulk, interface and surface, leading low charge separation/transport efficiencies. Recently, coupling of two materials, e.g., BiVO4/WO3, Fe2O3/WO3 and CuWO4/WO3, to form a type II heterojunction has been demonstrated to be a viable means to improve the PEC performance by enhancing the charge separation and transport efficiencies. In this study, we have prepared a triple-layer heterojunction BiVO4/WO3/SnO2 photoelectrode that shows a comparable PEC performance with previously reported best-performing nanostructured BiVO4/WO3 heterojunction photoelectrode via a facile solution method. Interestingly, we found that the incorporation of SnO2 nanoparticles layer in between WO3 and FTO largely promotes electron transport and thus minimizes interfacial recombination. The impact of the SnO2 interfacial layer was investigated in detail by TEM, hall measurement and electrochemical impedance spectroscopy (EIS) techniques. In addition, our planar-structured triple-layer photoelectrode shows a relatively high transmittance due to its low thickness (~300 nm), which benefits to couple with a solar cell to form a tandem PEC device. The overall PEC performance, especially the photocurrent onset potential (Vonset), were further improved by a reactive-ion etching (RIE) surface etching and electrocatalyst (CoOx) deposition.

• Fire Science and Engineering
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• v.26 no.5
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• pp.41-47
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• 2012

As a core process in the manufacture of state-of-the-art industrial technologies such as semiconductor and LCD, a clean room is the most important process which can affect the performance and quality of products drastically. Nevertheless, scientific research on comprehensive safety measures from a fire protection standpoint is not being carried out in Korea. This study aims to derive measures to improve smoke control systems by identifying performance and problems of smoke systems installed in clean rooms as an LCD manufacturing process and analyzing fire and evacuation simulations considering several scenarios. As a result of analysis of fires and smoke in a clean roomas an LCD manufacturing process, it is found to be necessary to stop air handling units through interlocking in case of a fire and exhaust smoke out of the room through the top of FAB in consideration of buoyancy of smoke. It is also found to be necessary to install quick response sprinkler heads and accessories to accelerate the response time, because the heat-accumulating performance of sprinkler heads decreases in this application. Despite its low density of dwelling due to the automation process, clean room is characterized by an array of complex production equipment and working environment requiring dustproof clothes, which makes it difficult to acquire evacuation safety performance. Thus, thorough control of danger factors in processes and periodic education and training are required. It is also necessary to establish a level of domestic technologies equivalent to the level of standards of advanced countries in fire protection.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.57
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• pp.283-303
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• 2013

When a trade conflict arises related to an officially supported export credit programme, The World Trade Organization(WTO), decides on whether the programme is a forbidden subsidy stipulated in the Agreement on Subsidies and Countervailing Measures(the ASCM Agreement). Korea was taken to the WTO panel two times for the export credit programme. One is the semiconductor case in 2002 and the other was the shipbuilding disputes in 2004. And, In 2012, the U.S. Commerce Department ruled K-SURE's export insurance for Korean refrigerator manufacturers as a forbidden subsidy even if the case was not taken to the WTO. This paper examines the significance of export credit programmes on the WTO ASCM Agreement and discusses how to operate these programmes so they would not infringe upon the Agreement by analyzing the actual cases of WTO subsidy conflicts that involved Korean enterprises in relation to export credit programmes for the purpose of determining the related issues and impacts. From this research the results were as follows: First, on whether export credit is a prohibited subsidy, the deciding factor was whether a benefit has been conferred to the beneficiary. On the presence of a benefit, the WTO panel used market benchmarks as the main criteria. Thus, official export credit agencies(ECAs) should be careful not to provide export credit support which had been granted to the beneficiary at better than market terms. Second, in the case of export credit, the special status of ECA as a public body receiving government support itself does not constitute a subsidy. However, caution must be taken not to provide export credit that may lead to WTO ASCM subsidy conflicts involving a certain exporter or industry by setting up clear and valid regulations and fair work processes in the operation of export credit programmes. Third, item (j) of Annex I cannot be interpreted reversely as this item is for interpreting the presence of a prohibited subsidy, not the presence of a benefit. Thus, an export credit program that confers a financial contribution, a benefit and specificity, could qualify as a prohibited subsidy. Fourth, ECAs not only have to maintain long-term account balance but also introduce additional measures to meet this long-term balance such as a clear and systematic premium system. Finally, export credit programmes that are not defined in item (j) of Annex I of the ASCM Agreement would not deemed as an prohibited export subsidy as long as the continued support of the programmes are not being forced.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.8
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• pp.909-914
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• 2007

Fluorine compounds are the essential chemicals for wet processes of semiconductor and LCD production line. Problems of conventional treatments for fluoride wastewater are their high operation costs and low fluoride removal capacity. In this study, cement paste containing various Ca-bearing hydrates such as portlandite, calcium silicate hydrate(CSH), and ettringite was investigated for fluoride removal. The objectives of this study are to assess the feasibility of using cement paste cured mixture of cement and water as an alternative agent for treatment of fluoride wastewater and to investigate fluoride removal capacity of the cement paste. The performance of cement paste was comparable to that of lime in the kinetic test. In column experiment where the effluent fluoride concentrations were below 0.5 mg/L. Then the leached calcium reached the maximum level of 800 mg/L. The nitrate reduced to the level of less than 10 mg/L. Nitrate in the wastewater was exchanged with interlayer sulfate of these cement hydrate LDHs. Phosphate concentration could be reduced to 10 mg/L by forming calcium phosphate. These results indicate that the cement paste generally has advantageous characteristics as an economical and viable substitute for lime to remove fluoride.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.356-362
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• 2013

An attempt has been made to optimize elongated rotating arc plasma $NH_3$ scrubber. Among diverse semiconductor processes, diffusion and implantation process inevitably produce $NH_3$ as byproduct and efficient dry process for the decomposition of $NH_3$ is required. Plasma process does not produce NOx that is commonly produced in combustion process and there is no problem of deactivation, usually experienced in catalyst process. However, plasma process uses electrical energy and needs to be optimized to achieve feasibility of application. In this work, mode control of rotating arc is presented as tentative solution for the possible optimization of the process. Based on existing rotating arc, scale-up and following mode mapping was tried. Proposed reactor design was evaluated in the $NH_3$ decomposition process and revealed that optimization scheme is at hand. In the experiment of full scale scrubber including heat exchanger, the process gave more stable and efficient process of $NH_3$ decomposition.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.948-954
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• 2008

Membrane bioreactor(MBR) processes have been widely applied to wastewater treatment for last decades due to its excellent capability of solid-liquid separation. However, membrane fouling was considered as a limiting factor in wide application of the MBR process. Excess aeration into membrane surface is a common way to control membrane fouling in most MBR. However, the excessively supplied air is easily dissipated in the reactor, which results in consuming energy and thus, it should be modified for effective control of membrane fouling. In this study, cylindrical tube was introduced to MBR in order to use the supplied air effectively. Membrane fibers were immersed into the cylindrical tube. This makes the supplied air non-dissipated in the reactor so that membrane fouling could be controlled economically. Two different air supplying method was employed and compared each other; nozzle and porous diffuser which were located just beneath the membrane module. Transmembrane pressure(TMP) was monitored as a function of airflow rate, flux, and ratio of the tube area and cross-sectioned area of membrane fibers(A$_m$/A$_t$). Flow rate of air and liquid was regulated to obtain slug flow in the cylindrical tube. With the same flow of air supply, nozzle was more effective for controlling membrane fouling than porous diffuser. Accumulation of sludge was observed in the tube with the nozzle, if the air was not suppled sufficiently. Reduction of membrane fouling was dependent upon the ratio, A$_m$/A$_t$. For diffuser, membrane fouling was minimized when A$_m$/A$_t$ was 0.27, but 0.55 for nozzle.

• The Journal of the Korea Contents Association
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• v.10 no.6
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• pp.329-335
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• 2010

Digital imaging detectors can use a variety of detection materials to convert X-ray radiation either to light or directly to electron charge. Many detectors such as amorphous silicon flat panels, CCDs, and CMOS photodiode arrays incorporate a scintillator screen to convert x-ray to light. The digital radiography systems based on semiconductor detectors, commonly referred to as flat panel detectors, are gaining popularity in the clinical & hospital. The X-ray detectors are described between a-Silicon based indirect type and a-Selenium based direct type. The DRS of detectors is used to convert the x-ray to electron hole pairs. Image processing is described by specific image features: Latitude compression, Contrast enhancement, Edge enhancement, Look up table, Noise suppression. The image features are tuned independently. The final enhancement result is a combination of all image features. The parameters are altered by using specific image features in the different several hospitals. The image in a radiological report consists of two image evaluation processes: Clinical image parameters and MTF is a descriptor of the spatial resolution of a digital imaging system. We used the edge test phantom and exposure procedure described in the IEC 61267 to obtain an edge spread function from which the MTF is calculated. We can compare image in the processing parameters to change between original and processed image data. The angle of the edge with respect to the axes of detector was varied in order to determine the MTF as a function of direction. Each MTF is integrated within the spatial resolution interval of 1.35-11.70 cycles/mm at the 50% MTF point. Each image enhancement parameters consists of edge, frequency, contrast, LUT, noise, sensitometry curve, threshold level, windows. The digital device is also shown to have good uniformity of MTF and image parameters across its modality. The measurements reported here represent a comprehensive evaluation of digital radiography system designed for use in the DRS. The results indicate that the parameter enables very good image quality in the digital radiography. Of course, the quality of image from a parameter is determined by other digital devices in addition to the proper clinical image.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.11-11
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• 2010

Thin-film-transistors (TFTs) that can be deposited at low temperature have recently attracted lots of applications such as sensors, solar cell and displays, because of the great flexible electronics and transparent. Transparent and flexible transistors are being required that high mobility and large-area uniformity at low temperature [1]. But, unfortunately most of TFT structures are used to be $SiO_2$ as gate dielectric layer. The $SiO_2$ has disadvantaged that it is required to high driving voltage to achieve the same operating efficiency compared with other high-k materials and its thickness is thicker than high-k materials [2]. To solve this problem, we find lots of high-k materials as $HfO_2$, $ZrO_2$, $SiN_x$, $TiO_2$, $Al_2O_3$. Among the High-k materials, $Al_2O_3$ is one of the outstanding materials due to its properties are high dielectric constant ( ~9 ), relatively low leakage current, wide bandgap ( 8.7 eV ) and good device stability. For the realization of flexible displays, all processes should be performed at very low temperatures, but low temperature $Al_2O_3$ grown by sputtering showed deteriorated electrical performance. Further decrease in growth temperature induces a high density of charge traps in the gate oxide/channel. This study investigated the effect of growth temperatures of ALD grown $Al_2O_3$ layers on the TFT device performance. The ALD deposition showed high conformal and defect-free dielectric layers at low temperature compared with other deposition equipments [2]. After ITO was wet-chemically etched with HCl : $HNO_3$ = 3:1, $Al_2O_3$ layer was deposited by ALD at various growth temperatures or lift-off process. Amorphous InGaZnO channel layers were deposited by rf magnetron sputtering at a working pressure of 3 mTorr and $O_2$/Ar (1/29 sccm). The electrodes were formed with electron-beam evaporated Ti (30 nm) and Au (70 nm) bilayer. The TFT devices were heat-treated in a furnace at $300^{\circ}C$ and nitrogen atmosphere for 1 hour by rapid thermal treatment. The electrical properties of the oxide TFTs were measured using semiconductor parameter analyzer (4145B), and LCR meter.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.10-17
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• 2018

POU (point of use) scrubbers were applied for the treatment of waste gases including PFCs (perfluorocompounds) exhausted from the CVD (chemical vapor deposition), etching, and cleaning processes of semiconductor and display manufacturing plant. The GWP (global warming potential) and atmosphere lifetime of PFCs are known to be a few thousands higher than that of $CO_2$, and extremely high temperature more than 3,000 K is required to thermally decompose PFCs. Therefore, POU gas scrubbers based on the thermal plasma technology were developed for the effective control of PFCs and industrial application of the technology. The thermal plasma technology encompasses the generation of powerful plasma via the optimization of the plasma torch, a highly stable power supply, and the matching technique between two components. In addition, the effective mixture of the high temperature plasma and waste gases was also necessary for the highly efficient abatement of PFCs. The purpose of this paper was to provide not only a useful technical information of the post-treatment process for the waste gas scrubbing but also a short perspective on R&D of POU plasma gas scrubbers.