• Korean Journal of Materials Research
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• v.15 no.8
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• pp.508-513
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• 2005

[ $TiO_2-Fe_2O_3$ ] nanocomposite powders for magnetic photocatalyst were synthesized by sol-gel process, in which $TiO_2$ photocatalytic layer was formed on the surface of $\gamma-Fe_2O_3$ magnetic core. Transmission electron microscopy (TEM) observation and X-ray diffractometry (XRD) analysis revealed that$\gamma-Fe_2O_3$ nanoparticles, $10\~20nm$ in diameter, were coated by $TiO_2$ shell of 5nm in thickness and $TiO_2$ was anatase phase. Also hydroxyl group (-OH) used to decompose organic compounds was detected by Fourier transformation infrared spectrometry(FT-IR) analysis. UV-Visible spectrophotometry results showed that light absorption occurred in the wavelength range of $400\~700 nm$, and the band gap energy $(E_g)$ of powder was 1.8 eV. Finally it was found that the coercivity $(H({ci})$ and saturation magnetization $(M_s)$ of the powder were 79 Oe and 14.8 emu/g, respectively as experimental vibrating sample magnetometer (VSM) measurements.

• Journal of Powder Materials
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• v.18 no.5
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• pp.449-455
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• 2011

In this study, p-type $(AgSbTe_2)_{15}(GeTe)_{85}$: TAGS-85 compound powders were prepared by gas atomization process, and then their microstructures and mechanical properties were investigated. The fabricated powders were of spherical shape, had clean surface, and illustrated fine microstructure and homogeneous $AgSbTe_2$ + GeTe solid solution. Powder X-ray diffraction results revealed that the crystal structure of the TAGS-85 sample was single rhombohedral GeTe phase, which with a space group $R_{3m}$. The grain size of the powder particles increased while the micro Vickers hardness decreased with increasing annealing temperature within the range of 573 K and 723 K due to grain growth and loss of Te. In addition, the crystal structure of the powder went through a phase transformation from rhombohedral ($R_{3m}$) at low-temperature to cubic ($F_{m-3m}$) at high-temperature with increasing annealing temperature. The micro Vickers hardness of the as-atomized powder was around 165 Hv, while it decreased gradually to 130 Hv after annealing at 673K, which is still higher than most other fabrication processes.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.25-28
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• 2010

The need for multiband RF front-end in modern communication system is growing rapidly. For example, satellite system always uses a complex arrangement of frequency plans and consequently needs filters for each communication channel and it will be ideal to have a single filter module that does jobs of all those channel filters to reduce the size and payload of the system. In this paper, a new method to transform four-port self-feedback balanced dual-band bandpass filter into two-port is proposed. The two-port balanced dual-band bandpass filter which has baluns at the input and output ports and the fundamental frequency at 2.5 GHz and the first harmonic frequency at 5.7 GHz is fabricated and measured. Good agreement between measured and simulated results was achieved.

• Tuberculosis and Respiratory Diseases
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• v.38 no.1
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• pp.25-33
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• 1991

The immune staus is known to be decreased in malignant disease and radiation therapy (RT), used as a therapeutic tool, further decrease this-attenuated immune status. We measured the number of peripheral lymphocytes, its subsets and lymphoblast transformation for PPD, PHA, monoclonal antibodies including anti-CD3 and anti-CD2 before and after RT in 19 patients with squamous cell lung cancer to search the fine mechanism behind the RT-induced attenuation of lymphoblast transformtion for mitogens and antigen. The results were as follows; 1) The number of lymphocytes and its subsets decreased significantly after RT, but the percentages of lymhocyte subsets did not change aftr RT except interleukin-2 receptor positive T lymphocytes. 2) The function of lymphoctes, measured by lymphoblast tranformation for PHA and PPD, decrased after RT and the compositions of PBMC used for lymphoblast transformtion were not different before and after RT. 3) The mitosis of lymphocytes to anti-CD2 or anti-CD3 decreased significantly after RT. And IL-2 plus anti-CD3 increased the mitosis than that of anti-CD3 only after RT, but before RT there was no difference. In conclusion, we suggested the fine mechanism behind the RT-induced attenuation of immune response might be the dysfunction of lymphocytes in terms of impaired synthesis of IL-2 rather than the decrease of circulating lymphocyte numbers.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.608-613
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• 2012

We investigated the property changes of MgO powders sintered at temperatures ranging from $700^{\circ}C$ to $1900^{\circ}C$ for 5minutes at a pressure of 2.7 GPa for a high-pressure high-temperature(HPHT) diamond synthesis process. The physical properties of the sintered MgO powders were characterized by optical microscopy, field emission scanning electron microscopy (FE-SEM), Vickers hardness tests, and by the apparent density, and X-ray diffractometry. An optical micro-analysis showed that white MgO powders became black after sintering due to carbon contamination from the graphite heat source. FE-SEM revealed the growth in the grain size of the MgO powders from $0.3{\mu}m$ to $50{\mu}m$ after sintering at $1700^{\circ}C$. The hardness and apparent density increased to $1800^{\circ}C$ while the samples were dedensified at $1900^{\circ}C$ due to the growth of isolated pores. According to the XRD analysis, no phase transformation occurred in the MgO powders. These results suggest that HPHT-sintered MgO powders can show an accelerated sintering process characterized by grain neck growth, pore connections, isolated pore growth and dedensification in 5 minutes, while these processes with the conventional sintering process take at least 5 hours.

• Archives of design research
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• v.17 no.1
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• pp.201-210
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• 2004

The web as a sign synthesis text has become a kernel for incorporeal knowledge as well as a communication model through the ubiquitous environment all over the world. The evaluation of the communication model, which is essential for the information structure, acts as an important basis on determining the quality of the web contents. In this study, the development of the progress of the communication of semantic meaning in the construction of the information structure was analyzed in views of the form, the function, and the emotional effect of the rich media contents of the web. The transformation process from the initial access elements through the final selection elements was suggested as the communication model and the effects of the function of the information in the web on the process was assessed by the engineering and linguistic models of Shannon, Weaver, and Roman Jakobson. The results of this study showed that the environments such as the speed, the memory space, data compression technique, and data filtering have influences on the web contents expression and the evaluation of the communication model in connection with the environments is the basis in the information structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.101-101
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• 2010

ZnO shows a direct band gap of 3.37eV, large exciton binding energy (~60 meV), high oxidation ability, high sensitivity to many gases, and low cost, and it has been used in various applications such as transparent electrodes, light emitting diodes (LEDs), gas sensors and photocatalysts. Among these applications ZnO as photocatalyst has considerably attracted attention over the past few years because of its high activities in removing organic contaminants generated from industrial activities. In this research, ZnO nanoparticles were synthesized by spray-pyrolysis method using the zinc acetate dihydrate as starting material at synthesis temperature of $900^{\circ}C$ with concentration varied from 0.01 to 1.0M. The physical and chemical properties of the synthesized ZnO nanoparticles were examined by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transformation Infrared (FT-IR), and UV-vis spectroscopy. The Miller indices of XRD patterns indicate that the synthesized ZnO nanoparticles showed a hexagonal wurtzite structure. With increased precursor concentration, a primary, secondary particle sizes of ZnO nanoparticles increased by 0.8 to $1.5{\mu}m$ and 15 to 35nm, and their crystallinity was improved. Methyleneblue (MB) solution ($1{\mu}M$) as a test comtaminant was prepared for evaluating the photocatalytic activities of ZnO nanoparticles synthesized in different precursor concentration. The results show that the photocatalytic efficiency of ZnO nanoparticles was gradually enhanced by increased precursor concentration.

• Korean Journal of Materials Research
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• v.21 no.11
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• pp.604-610
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• 2011

The effect of $BaF_2$ flux in $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) formation was investigated. Phase transformation of $Y_3Al_5O_{12}$(YAG) was characterized by using XRD, SEM, and TEM-EDS, and it was revealed that the sequential formation of the $Y_4Al_2O_9$(YAM), $YAlO_3$(YAP) and $Y_3Al_5O_{12}$(YAG) in the temperature range of 1000-1500$^{\circ}C$. Single phase of YAG was revealed from 1300$^{\circ}C$. In order to find out the effect of $BaF_2$ flux, three modeling experiments between starting materials (1.5$Al_2O_3$-2.5$Y_2O_3$, $Y_2O_3$-$BaF_2$, and $Al_2O_3$-$BaF_2$) were done. These modeling experiments showed that the nucleation process occurs via the dissolution-precipitation mechanism, whereas the grain growth process is controlled via the liquid-phase diffusion route. YAG:Ce phosphor particles prepared using a proposed technique exhibit a spherical shape, high crystallinity, and an emission intensity. According to the experimental results conducted in this investigation, 5% of $BaF_2$ was the best concentration for physical, chemical and optical properties of $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) that is approximately 10-15% greater than that of commercial phosphor powder.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.1013-1021
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• 2020

A combination of simultaneous thermal analysis, evolved gas analysis and non-ambient XRD techniques was used to characterise and investigate the conversion reactions of ammonium uranates into uranium oxides. Two solid phases of the ternary system NH₃ - UO₃ - H₂O were synthesised under specified conditions. Microspheres prepared by the sol-gel method via internal gelation were identified as 3UO₃·2NH₃·4H₂O, whereas the product of a typical ammonium diuranate precipitation reaction was associated to the composition 3UO₃·NH₃·5H₂O. The thermal decomposition profile of both compounds in air feature distinct reaction steps towards the conversion to U₃O₈, owing to the successive release of water and ammonia molecules. Both compounds are converted into α-U₃O₈ above 550 ℃, but the crystallographic transition occurs differently. In compound 3UO₃·NH₃·5H₂O (ADU) the transformation occurs via the crystalline β-UO₃ phase, whereas in compound 3UO₃·2NH₃·4H₂O (microspheres) an amorphous UO₃ intermediate was observed. The new insights obtained on these uranate systems improve the information base for designing and synthesising minor actinide-containing target materials in future applications.

• International Journal of Computer Science & Network Security
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• v.21 no.5
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• pp.57-68
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• 2021

Successfully adapting to digital and customer-oriented transformation, the concept of lean manufacturing professes the philosophy of creating greater benefit while minimizing losses. These losses are operations that do not add value in the production process to ensure the efficiency, flexibility, and profitability of projects. In the context of broad automation and digitalization of all sectors of the economy, mechanisms for combining automation technologies and lean production are becoming available. Moreover, when it comes to the efficient use of financial, human, or material resources, it is clear that the use of Industry 4.0 technologies can be an effective tool for achieving the goals of lean production, as many of them pursue the same goal. In this context, this article aims to study the effectiveness of the implementation of project management concepts at the global level and identify the main factors influencing its effectiveness to ensure the achievement of lean production through LEAN technologies and Industry 4.0 technologies. To achieve this goal, several statistical indicators were selected and several statistical methods of analysis were used: pairwise correlation, regression analysis, methods of comparison, synthesis, and generalization. Statistical analysis was conducted according to a survey conducted by the Project Management Institute (PMI) in 2020. An economic-mathematical model of dependence of project effectiveness in different regions of the world on the level of implementation of project management approaches is built, which shows that the increase in project effectiveness by 85% is due to financial losses, technical training, and consumer orientation. These results allow project managers to develop appropriate strategies to improve project management approaches at all levels. It is established that LEAN technologies and technologies of Industry 4.0 have several tools that have a positive effect on minimizing losses following the concept of lean production. Besides, given that the technology of Industry 4.0 is focused on the automation of Lean Production technology, a mechanism for the introduction of lean production using these technologies and methods.