• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.39.2-39.2
• /
• 2011

The new and renewable energy today has a great interest in all countries around the world. In special it has need more limit of the fossil fuel that needs of low carbon emission among the social necessary conditions. Recently, the high-rise building demand the structural safety, the economic feasibility and the functional design. The high-rise building spends enormous energy and it satisfied the design in solving energy requirements. The requirements of energy for the building depends on the partly form wind energy due to the cladding of the building that came from the surroundings of the high-rise building. In this study of the wind energy, the cladding of the building was assessed a tentative study. The wind energy obtains from several small wind powers that came from the building or the surrounding of the building. In making a cladding the wind energy forms with wind pressure by means of energy transformation methods. The assessment for the building cladding was surrounded of wind speed and wind pressure that was carried out as a result of numerical simulation of wind environment and wind pressure which is coefficient around the high-rise building with the computational fluid dynamics. In case of the obtained wind energy from the pressure of the building cladding was estimated by the simulation of CFD of the building. The wind energy at this case was calculated by energy transform methods: the wind pressure coefficients were obtained from the simulated model for wind environment using CFD as follow. The concept for the factor of $E_f$ was suggested in this study. $$C_p=\frac{P_{surface}}{0.5{\rho}V^{2ref}}$$ $$E_c=C_p{\cdot}E_f$$ Where $C_p$ is wind pressure coefficient from CFD, $E_f$ means energy transformation parameter from the principle of the conservation of energy and $E_c$ means energy from the building cladding. The other wind energy that is $E_p$ was assessed by wind power on the building or building surroundings. In this case the small wind power system was carried out for wind energy on the place with the building and it was simulated by computational fluid dynamics. Therefore the total wind energy in the building was calculated as the follows. $$E=E_c+E_p$$ The energy transformation, which is $E_f$ will need more research and estimation for various wind situation of the building. It is necessary for the assessment to make a comparative study about the wind tunnel test or full scale test.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.8
• /
• pp.5550-5558
• /
• 2015

Recently, fuel cell with high energy efficiency and low CO2 emission is energetically interconnected with power system. Especially, FCGS(Fuel Cell Generation System) which usually operates at high temperature, is being developed and installed in the form of large scale system. However, it is reported that power system disturbances related to surge, harmonic and EMI have caused several problems such as malfunction of protection device and damage of control device in the large scale FCGS. In order to solve these problems, this paper presents a modeling of operation characteristics of FCGS by PSCAD/EMTDC, ETAP, P-SIM software. And also, this paper proposes countermeasure algorithms to prevent power system disturbances. From the simulation results, it is confirmed that the proposed algorithm is useful method for the stable operation of large scale FCGS.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.5
• /
• pp.118-124
• /
• 2011

To reach the Euro-6 regulations of PM and $NO_x$ for light-duty diesel vehicles, it will be necessary to apply the CDPF and the de-$NO_x$ catalyst. The described system consists of a catalytic configuration, where the CDPF is placed downstream of the diesel engine and followed by a urea injection unit and a urea-SCR catalyst. One of the advantages of this system configuration is that, in this way, the SCR catalyst is protected from PM, and both white PM and deposits become reduced. In the urea-SCR system, the injection control of reductant is the most important thing in order to have good performance of $NO_x$ reduction. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency become slower, due to temperature window of SCR catalyst. And space velocity also affects to $NO_x$ conversion efficiency. In this paper, rig-tests were performed to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the urea-SCR system. And vehicle test was performed to verify control strategy of reductatnt injection. The developed control strategy of reductant injection was improved over all $NO_x$ reduction efficiency and $NH_3$ consumption in urea-SCR system. Results of this paper contribute to develop urea-SCR system for light-duty vehicles to meet Euro-5 emission regulations.

• Journal of Energy Engineering
• /
• v.10 no.3
• /
• pp.195-205
• /
• 2001

A great deal of energy is necessary with emission of lots of wastewater in dyeing and finishing process, but heat recovery from wastewater is not introduced since is technology is not developed yet. In order to obtain the method utilizing hot water produced by heat source, that is, dyeing wastewater it was investigated the characteristics of dyeing and finishing process and energy basic unit. Energy basic unit of polyester/cotton (T/C), polyester/rayon (T/R) and polyester dyeing process are higher than that of the other process. The average quantity of wastewater for each dyeing company is 20,470 ton/month, the average temperature of wastewater is about 41$^{\circ}C$. Because the SS solution of wastewater in polyester dyeing process is lower than that of the other process, the effect of corrosion in heat recovery system is low. Since the energy price for 1000 kcal produced by vapor compression heat pump is presumed to be 22.50 won, it is found to be very economic heat recovery system, and its payback is 2.09 years for the factory with LNG boiler.

• Korean Journal of Construction Engineering and Management
• /
• v.14 no.4
• /
• pp.55-64
• /
• 2013

As GHG target management is introduced in Korea, designated establishment takes responsibilities to reduce more than 30% of expected GHG emission until 2020. Although decreasing GHG has been requested to universities which consume great amount of energy, there are difficulties to apply high cost countermeasures. Therefore, this research suggest a low cost, easily-applicable energy saving method, and derive potential GHG reduction amount in the case of SNU, Kwan-ak campus. First of all, 11 rooms of different use were chosen as the samples, and energy consumption in each room was measured. Standard models for each room were built through researching on the electric devices in each room. Moreover, energy consumption was computed for each devices through analyzing the pattern of electricity consumption. 32 GHG reduction technology and action program were chosen, and they were applied to the standard models for individual rooms. Through multiplying energy reduction rate of each program to energy consumption of each electric device, maximum energy reduction of each electric device is derived. Through that, Maximum GHG reduction for individual rooms and each month and the total GHG reduction capacity of Kwan-ak campus were computed. It was found out that approximately $5,311tCO_2$-eq can be reduced, when reduction technology and action program suggested by this research are applied. It appeared 24.48% of requested reduction amount to SNU can be reduced, till 2016.

• Clean Technology
• /
• v.18 no.3
• /
• pp.229-249
• /
• 2012

At present, global warming and depletion of fossil fuels have been one of the big issues which should be solved for sustainable development in the future. CCS (carbon capture and sequestration) technology as the post $CO_2$ reduction technology has been considered as a promising solution for global warming due to increased carbon emission. However, the environmental and ecological effects of CCS have drawn concerns. There are needs for noble post reduction technology. More recently, CCU (carbon capture and utilization) Technology, which emphasizes transforming carbon dioxide into value-added chemicals rather than storing it, has been attracted attentions in terms of preventing global warming and recycling the renewable carbon source. In this paper, various technologies developed for carbon dioxide conversion both in gas and liquid phase have been reviewed. For the thermochemical catalysis in gas phase, the development of the catalytic system which can be performed at mild condition and the separation and purification technology with low energy supply is required. For the photochemical conversion in liquid phase, efficient photosensitizers and photocatalysts should be developed, and the photoelectrochemical systems which can utilize solar and electric energy simultaneously are also in development for more efficient carbon dioxide conversion. The energy needed in CCU must be renewable or unutilized one. CCU will be a key connection technology between renewable energy and bio industry development.

• Corrosion Science and Technology
• /
• v.8 no.4
• /
• pp.162-169
• /
• 2009

Pure titanium and its alloys are drastically used in implant materials due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus than cortical bone. Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. For this reason, Ti-30Ta-xZr alloy systems have been studied in this study. The Ti-30Ta containing Zr(5, 10 and 15 wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24 hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and Ti coating and then coated with TiN, respectively, by using DC magnetron sputtering method. The analyses of coated surface were carried out by field emission scanning electron microscope(FE-SEM). The electrochemical characteristics were examined using potentiodynamic (- 1500 mV~+ 2000 mV) and AC impedance spectroscopy(100 kHz~10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The equiaxed structure was changed to needle-like structure with increasing Zr content. The surface defects and structures were covered with TiN/Ti coated layer. From the polarization behavior in 0.9% NaCl solution, The corrosion current density of Ti-30Ta-xZr alloys decreased as Zr content increased, whereas, the corrosion potential of Ti-30Ta-xZr alloys increased as Zr content increased. The corrosion resistance of TiN/Ti-coated Ti-30Ta-xZr alloys were higher than that of the TiN-coated Ti-30Ta-xZr alloys. From the AC impedance in 0.9% NaCl solution, polarization resistance($R_p$) value of TiN/Ti coated Ti-30Ta-xZr alloys showed higher than that of TiN-coated Ti-30Ta-xZr alloys.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03a
• /
• pp.16-16
• /
• 2010

GaN-based light-emitting diodes (LEDs) are attracting great interest as candidates for next-generation solid-state lighting, because of their long lifetime, small size, high efficacy, and low energy consumption. However, for general illumination applications, the external quantum efficiency of LEDs, determined by the internal quantum efficiency (IQE) and the light extraction efficiency, must be further increased. The IQE is determined by crystal quality and epitaxial layer structure and high value of IQE more than 70% for blue LEDs have been already reported. However, there is much room for improvement of light extraction efficiency because most of the generated photons from active layer remain inside LEDs by total internal reflection at the interface of semiconductor with air due to the high refractive index difference between LEDs epilayer (for GaN, n=2.5) and air (n=1). The light confining in LEDs will be reabsorbed by the metal electrode or active layer, reducing the efficacy of LEDs. Here, we present the first demonstration of enhanced light extraction by forming a MgO nano-pyramids structure on the surface of vertical-LEDs. The MgO nano-pyramids structure was successfully fabricated at room temperature using conventional electron-beam evaporation without any additional process. The nano-sized pyramids of MgO are formed on the surface during growth due to anisotropic characteristics between (111) and (200) plane of MgO. The ZnO layer with quarter-wavelength in thickness is inserted between GaN and MgO layers to increase the critical angle for total internal reflection, because the refractive index of ZnO (n=1.94) could be matched between GaN (n=2.5) and MgO (n=1.73). The MgO nano-pyramids structure and ZnO refractive-index modulation layer enhanced the light extraction efficiency ofV-LEDs with by 49%, comparing with the V-LEDs with a flat n-GaN surface. The angular-dependent emission intensity shows the enhanced light extraction through the side walls of V-LEDs as well as through the top surface of the n-GaN, because of the increase in critical angle for total internal reflection as well as light scattering at the MgO nano-pyramids surface.

• Journal of Conservation Science
• /
• v.30 no.3
• /
• pp.249-261
• /
• 2014

This study aims to examine production technique of white wares from the Guyre-2ri 1st and 2nd kiln sites, Wonju, Gangwon Province and characteristics of the used materials, and to find a correlation among materials of the excavated white wares. X-ray fluorescence sequential spectroscopy(XRF), X-ray diffraction(XRD), Dilatometer and Inductively coupled plasma mass spectrometry(ICP-MS), Inductively coupled plasma automic emission spectrometer(ICP-AES) were applied to determine the chemical composition, crystalline phase of samples, firing temperatures, trace elements and rare earth elements. White wares from the Guyre-2ri kiln sites contained high contents of coloring oxides and fluxes. Though firing temperature of each sample was different, they were mostly fired at a temperature below $1200^{\circ}C$ and some of them experienced a low temperature of $1000^{\circ}C{\pm}20^{\circ}C$ and a high temperature above $1200^{\circ}C$. When analyzing body crystalline phases of the white wares using the XRD method, quartz and mullite were extracted from all the samples, and the proportions were similar to each other. When analyzing the excavated white wares using the Seger formula, also, all the samples showed similar clay sources and production techniques. Moreover, the white wares were made of host rocks of the same geological origin, according to the result of rare earth elements analysis.

• Journal of Microbiology and Biotechnology
• /
• v.21 no.9
• /
• pp.893-902
• /
• 2011

Endophytic fungi are little known for their role in gibberellins (GAs) synthesis and abiotic stress resistance in crop plants. We isolated 10 endophytes from the roots of field-grown soybean and screened their culture filtrates (CF) on the GAs biosynthesis mutant rice line - Waito-C. CF bioassay showed that endophyte GMH-1B significantly promoted the growth of Waito-C compared with controls. GMH-1B was identified as Penicillium minioluteum LHL09 on the basis of ITS regions rDNA sequence homology and phylogenetic analyses. GC/MS-SIM analysis of CF of P. minioluteum revealed the presence of bioactive $GA_4$ and $GA_7$. In endophyte-soybean plant interaction, P. minioluteum association significantly promoted growth characteristics (shoot length, shoot fresh and dry biomasses, chlorophyll content, and leaf area) and nitrogen assimilation, with and without sodium chloride (NaCl)-induced salinity (70 and 140 mM) stress, as compared with control. Field-emission scanning electron microcopy showed active colonization of endophyte with host plants before and after stress treatments. In response to salinity stress, low endogenous abscisic acid and high salicylic acid accumulation in endophyte-associated plants elucidated the stress mitigation by P. minioluteum. The endophytic fungal symbiosis of P. minioluteum also increased the daidzein and genistein contents in the soybean as compared with control plants, under salt stress. Thus, P. minioluteum ameliorated the adverse effects of abiotic salinity stress and rescued soybean plant growth by influencing biosynthesis of the plant's hormones and flavonoids.