• Nuclear Engineering and Technology
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• v.34 no.1
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• pp.42-59
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• 2002

In order to transmute long-lived radioactive nuclides such as transuranics(TRU), Tc-99, and I- l29 in LWR spent fuel, a preliminary conceptual design study has been performed for the accelerator driven subcritical reactor system, called HYPER(Hybrid Power Extraction Reactor) The core has a hybrid neutron energy spectrum: fast and thermal neutrons for the transmutation of TRU and fission products, respectively. TRU is loaded into the HYPER core as a TRU-Zr metal form because a metal type fuel has very good compatibility with the pyre- chemical process which retains the self-protection of transuranics at all times. On the other hand, Tc-99 and I-129 are loaded as pure technetium metal and sodium iodide, respectively. Pb-Bi is chosen as a primary coolant because Pb-Bi can be a good spallation target and produce a very hard neutron energy spectrum. As a result, the HYPER system does not have any independent spallation target system. 9Cr-2WVTa is used as a window material because an advanced ferritic/martensitic steel is known to have a good performance under a highly corrosive and radiation environment. The support ratios of the HYPER system are about 4∼5 for TRU, Tc-99, and I-129. Therefore, a radiologically clean nuclear power, i.e. zero net production of TRU, Tc-99 and I-129 can be achieved by combining 4 ∼5 LWRs with one HYPER system. In addition, the HYPER system, having good proliferation resistance and high nuclear waste transmutation capability, is believed to provide a breakthrough to the spent fuel problems the nuclear industry is faced with.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.875-883
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• 2015

The use of subcritical aqueous homogenous reactors driven by accelerators presents an attractive alternative for producing $^{99}Mo$. In this method, the medical isotope production system itself is used to extract $^{99}Mo$ or other radioisotopes so that there is no need to irradiate common targets. In addition, it can operate at much lower power compared to a traditional reactor to produce the same amount of $^{99}Mo$ by irradiating targets. In this study, the neutronic performance and $^{99}Mo$, $^{89}Sr$, and $^{131}I$ production capacity of a subcritical aqueous homogenous reactor fueled with low-enriched uranyl nitrate was evaluated using the MCNPX code. A proton accelerator with a maximum 30-MeV accelerating power was used to run the subcritical core. The computational results indicate a good potential for the modeled system to produce the radioisotopes under completely safe conditions because of the high negative reactivity coefficients of the modeled core. The results show that application of an optimized beam window material can increase the fission power of the aqueous nitrate fuel up to 80%. This accelerator-based procedure using low enriched uranium nitrate fuel to produce radioisotopes presents a potentially competitive alternative in comparison with the reactor-based or other accelerator-based methods. This system produces ~1,500 Ci/wk (~325 6-day Ci) of $^{99}Mo$ at the end of a cycle.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.1
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• pp.115-128
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• 2019

Small and Medium-sized Enterprises (SMEs) are being faced with rapid changes in their business environments due to evolution of technologies and innovation in societal eco-systems. Particularly, dynamic interactions between such environments and enterprise activities have become significant, so technology planning, which is a process of identifying appropriate directions regarding product and technology development, has received much attention to cope with such dynamics proactively. However, SMEs typically have limits in performing independent, strategical and systematical technology planning activities due to the lack of human, material and financial resources. This paper proposes the development of a product roadmapping method so that SMEs carry out efficient technology planning activities with interconnections of external business environments. The present work provides product roadmap templates that directly accommodate the influence of business environments on the product's system and its associated super/sub-systems with the use of external environment analysis techniques including TRIZ methodology, PEST and 5Forces analysis. These templates are useful to efficiently forecast the directions of product's development and evolution, which arise from changes in external environments. Consequently, the present work enables SMEs to flexibly cope with the era of the next R&D generation, which pursues value creation through mutual interconnection between business environments and technology development.

• Smart Structures and Systems
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• v.30 no.3
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• pp.327-332
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• 2022

In building envelope, transparent components play an important role. The structural glazing systems are the weak element of the casing in terms of mechanical resistance, thermal and acoustic insulation. In the present work, new structural glass panels with granular aerogel in interspace were investigated from different points of view. In particular, the mechanical characterization was carried out in order to assess the resistance to bending of the single glazing pane. To this end, a special instrument system was built to define an alternative configuration of the coaxial double ring test, able to predict the fracture strength of glass large samples (400 × 400 mm) without overpressure. The thermal and lighting performance of an innovative double-glazing façade with granular aerogel was evaluated. An experimental campaign at pilot scale was developed: it is composed of two boxes of about 1.60 × 2 m² and 2 m high together with an external weather station. The rooms, identical in terms of size, construction materials, and orientation, are equipped with a two-wing window in the south wall surface: the first one has a standard glazing solution (double glazing with air in interspace), the second room is equipped with the innovative double-glazing system with aerogel. The indoor mean air temperature and the surface temperature of the glass panes were monitored together with the illuminance data for the lighting characterization. Finally, a brief energy characterization of the performance of the material was carried out by means of dynamic simulation models when the proposed solution is applied to real case studies.

• Smart Structures and Systems
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• v.29 no.2
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• pp.301-309
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• 2022

Protective coatings are most widely used anticorrosive structures for steel structures. The corrosion under the coating damages the host material, but this damage is completely hidden. Therefore, a field-applicable under-coating-corrosion visualization method has been desired for a long time. Laser ultrasonic technology has been studied in various fields as an in situ nondestructive inspection method. In this study, a comparative analysis was carried out between a guided-wave ultrasonic propagation imager (UPI) and pulse-echo UPI, which have the potential to be used in the field of under-coating-corrosion management. Both guided-wave UPI and pulse-echo UPI were able to successfully visualize the corrosion. Regarding the field application, the guided-wave UPI performing Q-switch laser scanning and piezoelectric sensing by magnetic attachment exhibited advantages owing to the larger distance and incident angle in the laser measurement than those of the pulse-echo UPI. Regarding the corrosion visualization methods, the combination of adjacent wave subtraction and variable time window amplitude mapping (VTWAM) provided acceptable results for the guided-wave UPI, while VTWAM was sufficient for the pule-echo UPI. In addition, the capability of multiple sensing in a single channel of the guided-wave UPI could improve the field applicability as well as the relatively smaller size of the system. Thus, we propose a guided-wave UPI as a tool for under-coating-corrosion management.

• Geomechanics and Engineering
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• v.32 no.1
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• pp.49-68
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• 2023

The three-dimensional failure criterion is essential for maintaining wellbore stability and sand production problem. The convenient factor for a stable wellbore is mud weight and borehole orientation, i.e., mud window design and selection of borehole trajectory. This study proposes a new three-dimensional failure criterion with linear relation of three in-situ principal stresses. The number of failure criteria executed to understand the phenomenon of rock failure under in-situ stresses is the Mohr-Coulomb criterion, Hoek-Brown criterion, Mogi-Coulomb criterion, and many more. A new failure criterion is the extended Mohr-Coulomb failure criterion with the influence of intermediate principal stress (σ₂). The influence of intermediate principal stress is considered as a weighting of (σ₂) on the mean effective stress. The triaxial compression test data for eleven rock types are taken from the literature for calibration of material constant and validation of failure prediction. The predictions on rock samples using new criteria are the best fit with the triaxial compression test data points. Here, Drucker-Prager and the Mogi-Coulomb criterion are also implemented to predict the failure for eleven different rock types. It has been observed that the Drucker-Prager criterion gave over prediction of rock failure. On the contrary, the Mogi-Coulomb criterion gave an equally good prediction of rock failure as our proposed new 3D failure criterion. Based on the yield surface of a new 3D linear criterion it gave the safest prediction for the failure of the rock. A new linear failure criterion is recommended for the unique solution as a linear relation of the principal stresses rather than the dual solution by the Mogi-Coulomb criterion.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.36 no.3
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• pp.137-148
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• 2018

Li Yu's Xian Qing Ou Ji was written during the late Ming and early Qing Dynasty when material culture flourished due to the development of the commercial economy. Xian Qing Ou Ji is considered a retrospective work that reflects the rich material society at that time. This study focuses on his gardening theories through the interpretation and analysis of these two texts of 'Jushibu(居室部)' and 'Zhongzhibu(種植部)' in Xian Qing Ou Ji. The results are summarized as follows. First, he explained the method of garden configuration and orientation according to the topography utilizing the theory of 'suiting one's measures to local conditions(因地制宜)'. He emphasized the detailed understanding of topography as the starting point for all the gardening theories. It stated that he tried to adjust the height of the terrain artificially to create an ideal form of 'anterior high and posterior low(前低後高)'. The successful arrangement of houses, pavilions, rockery and waterways et al. was able to be achieved because of his accurate understanding of topography. Second, 'borrowing scenery(取景在借)' means 'borrowing the outside scenery to the inside'. He applied this theory by 'viewing in motion(動觀)' and 'viewing in repose(靜觀)'. 'Viewing in motion' is seen as a positive methodology for landscape enjoyment. For example, the view through a window changes with movements of the boat, and it can portray thousands of landscape paintings which can be seen through the windows. In the case of 'viewing in repose', the window is regarded as a means of attracting outside garden views to the inside. Third, he emphasized 'the firmness of objects(制體宜堅)', where the design of windows and railings must be considered ahead of others. Fourth, he interpreted the contents of 'the pursuit of novelty(創異標新)'. This generalizes the characteristics of his gardening theory. The contents included 'hall wall(廳壁)', 'variable sun visor(活?)', 'hanging boards and couplets(聯?)' and 'method of supporting vines with bamboo screen(竹屛扶植法)'.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.251-251
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• 2016

For several decades, industrial processes consume a huge amount of raw water for various objects that consequently results in the generation of large amounts of wastewater. Wastewaters are consisting of complex mixture of different inorganic and organic compounds and some of them can be toxic, hazardous and hard to degrade. These effluents are mainly treated by conventional technologies such are aerobic and anaerobic treatment and chemical coagulation. But, these processes are not suitable for eliminating all hazardous chemical compounds form wastewater and generate a large amount of toxic sludge. Therefore, other processes have been studied and applied together with these techniques to enhance purification results. These include photocatalysis, absorption, advanced oxidation processes, and ozonation, but also have their own drawbacks. In recent years, electrochemical techniques have received attention as wastewater treatment process that could be show higher purification results. Among them, boron doped diamond (BDD) attract attention as electrochemical electrode due to good chemical and electrochemical stability, long lifetime and wide potential window that necessary properties for anode electrode. So, there are many researches about high quality BDD on Nb, Ta, W and Si substrates, but, their application in effluents treatment is not suitable due to high cost of metal and low conductivity of Si. To solve these problems, Ti has been candidate as substrate in consideration of cost and property. But there are adhesion issues that must be overcome to apply Ti as BDD substrate. Al, Cu, Ti and Nb thin films were deposited on Ti substrate to improve adhesion between substrate and BDD thin film. In this paper, BDD films were deposited by hot filament chemical vapor deposition (HF-CVD) method. Prior to deposition, cleaning processes were conducted in acetone, ethanol, and isopropyl alcohol (IPA) using sonification machine for 7 min, respectively. And metal layer with the thickness of 200 nm were deposited by DC magnetron sputtering (DCMS). To analyze microstructure X-ray diffraction (XRD, Bruker gads) and field emission scanning electron microscopy (FE-SEM, Hitachi) were used. It is confirmed that metal layer was effective to adhesion property and improved electrode property. Electrochemical measurements were carried out in a three electrode electrochemical cell containing a 0.5 % H2SO4 in deionized water. As a result, it is confirmed that metal inter layer heavily effect on BDD property by improving adhesion property due to suppressing formation of titanium carbide.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.21-26
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• 2002

A supercapacitor was developed using an amorphous ruthenium oxide material. The electrode of supercapacitor was prepared using an amorphous ruthenium oxide, which was synthesized from ruthenium trichloide hydrate$(RuCl_3{\cdo5}xH_2O)$. Thin film of tantalum was used as a current collector because it had wide. potential window characteristics than titanium and 575304 materials. A supercapacitor was assembled with ruthenium oxide as an electrode active material and 4.8M sulfuric acid solution as an electrolyte. The specific capacitance of the electrode was tested by a cyclic voltammetry using a half cell. The maximum differential specific capacitances during the oxidative and the reductive scans were 710 and $645\;F/g-RuO_2{\cdot}nH_2O$, respectively. The average specific capacitance was $521\;F/g-RuO_2{\cdot}nH_2O$. The assembled supercapacitor was protonated to the potential level of 0.5V vs. SCE. Super-capacitor, which was adjusted to the appropriate protonation level, had the specific capacitance of $151\;F/g-RuO_2{\cdot}nH_2O$ based on the concept of full cell.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.133-142
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• 1997

Most of the greenhouses employ the roll-up type ventilation control system. Torque required to roll-up and down might be theoretically expressed with the weight times radius of the ventilation roll; however, measured torques were two times of the theoretically estimated values. As the window film of roll-up vent is used over the periods of time, the warping and crumpling of the material caused the increase of the torque in addition to a span deformation. Therefore, this study was performed to develop an empirical torque formulae to present basic torque data and to assist the development of roll-up type ventilation control system. The empirically adjusted rolling radius (r＋a) exponentially increased at the maximum span deformation. The coefficient of rolling resistance (Cr) was about 0.7―0.8 depending upon the wrinkle status of film material.