• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.789-794
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• 2011

A coaxial-cable impedance transformer used in wideband frequency range is generally restricted to the fixed impedance transformation ratio as n2:1 or 1:n2(n: the number of coaxial cables). In this paper, we propose a new coaxial-cable impedance transformer to have an arbitrary impedance transformation ratio. We have fabricated three impedance transformers($50-{\Omega}$ to $25-{\Omega}$, $50-{\Omega}$ to $20-{\Omega}$ and $50-{\Omega}$ to $9-{\Omega}$) to confirm the operation characteristic of the suggested impedance transformer. The reflection characteristics (S11) of the fabricated $50-{\Omega}$ to $25-{\Omega}$ and $50-{\Omega}$ to $20-{\Omega}$ impedance transformer were less than -15dB over about 3-octaves frequency range and the reflection characteristic (S11) of the fabricated $50-{\Omega}$ to $9-{\Omega}$ impedance transformer was less than -15dB over about 1-octave frequency range, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.661-668
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• 2012

A coaxial-cable impedance transformer that can be used in high power and wideband frequency range is an arbitrary impedance transformation ratio by an additional coaxial cable. The coaxial-cable impedance transformer to be 50-${\Omega}$ to 25-${\Omega}$ impedance transformation ratio is easily operated an wideband power divider by connecting two 50-${\Omega}$ lines at 25-${\Omega}$ impedance point. This wideband power divider has a poor output matching characteristic and a poor isolation characteristic between two output ports. In this paper, it proposes a coaxial-cable power divider to be a good output matching and isolation characteristics as it uses the singly terminated filter design theory. The odd-mode operation characteristic of the suggested power divider to use singly terminated low pass filter coefficient due to matching order and ripple value is examined by ADS program. And, it fabricates and measures the operation characteristic of 2-way power divider with 2nd-order and 4th-order matching circuit.

• Journal of Powder Materials
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• v.23 no.5
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• pp.353-357
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• 2016

In this study, $TiO_2$ powders are synthesized from ammonium hexafluoride titanate (AHFT, $(NH_4)_2TiF_6$) as a precursor by heat treatment. First, we evaluate the physical properties of AHFT using X-ray diffraction (XRD), particle size analysis (PSA), thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FE-SEM). Then, to prepare the $TiO_2$ powders, is heat-treated at $300-1300^{\circ}C$ for 1 h. The ratio of anatase to rutile phase in $TiO_2$ is estimated by XRD. The anatase phase forms at $500^{\circ}C$ and phase transformation to the rutile phase occurs at $1200^{\circ}C$. Increase in the particle size is observed upon increasing the reaction temperature, and the phase ratio of the rutile phase is determined from a comparison with the calculated XRD data. Thus, we show that anatase and rutile $TiO_2$ powders could be synthesized using AHFT as a raw material, and the obtained data are utilized for developing a new process for producing high-quality $TiO_2$ powder.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.580-587
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• 1996

Synthesis of long fibrous $K_2Ti_4O_9$ was attempted to find a method to produce long fibrous $K_2Ti_6O_{13}$ and other derivatives and also phase transformation of $K_2Ti_4O_9$ synthesized was investigated. Long fibrous $K_2Ti_4O_9$ was succesively synthesized by the calcination reaction under the following reaction conditions ; reaction temperature of $1050^{\circ}C$, $TiO_2$ mole ratio to $K_2CO_3$ of 2.8 and reaction time of 3hrs, and scattering of calcined products for 10hrs with hot boiling water. $K_2Ti_4O_9$ showed lower structural stability under heat treatment and the structure of $K_2Ti_4O_9$ was converted to $K_2Ti_6O_{13}$ under heating temperature of over $250^{\circ}C$.

• Journal of the Korea Institute of Building Construction
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• v.22 no.4
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• pp.379-390
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• 2022

While the construction industry is striving to make changes suitable for the 4th industrial revolution era through the introduction of 4th industrial revolution technologies, such change is progressing more slowly than in other industries. Nevertheless, the recent digitization and digital transformation of the construction industry can provide a new paradigm to address and innovate the chronic problems faced by the construction industry. Therefore, in this study, a case study using a data hub and API for use of the data hub, which is essential for digitalization and digital transformation, was conducted, and the efficiency and feasibility of using the data hub and API were considered. When the API system was introduced, it was found that the average budget savings per person was about 23%, and the costbenefit ratio was about 4.4 times higher, indicating that the feasibility of the project was very high. The results and framework of this study can serve as fundamental research data for related research, and provide a worthy case study to promote the introduction of related technologies. This will ultimately contribute to digitalization and digital transformation for smartization of the construction industry.

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.280-286
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• 1998

LaAlO3 Single crystals used as a substrate for thin film depositions of a high temperature oxide su-perconductor YB2Cu3O7 and applied to microwave frequencies were grown by the Traveling Solvent Flati-ing Zone (TSFZ) method and characterized. For the growth of LaAlO3 single crystals polycrystalline fe-edrods were prepared from powder mixture of La2O3 and Al2O3 with a mole ratio of 1:1 calcined at 110$0^{\circ}C$ for 3h and sintered at 140$0^{\circ}C$ for 4h The growth LaAlO3 crystals was 4-5mm in diameter 30mm in length and dark brown. The growth rate was 2-3mm/h and the rotation speeds were 10rpm for an upper ro-tation and 40 rpm for a lower rotation The growing crystals and the feedrods were counter-rotated. The orientation of the grown single crystals of LaAlO3 was identified to be [111] direction. Dielectric constants were measured to be 30-33 between 100 kHz and 1 MHz in the 30$0^{\circ}C$ to 45$0^{\circ}C$ temperature range and 102 in a range of 100 kHz at the phase transformation temperature of 522$^{\circ}C$ Dielectric losses were calculated to be 1.8$\times$10-4 at the room temperature and 5.7$\times$10-3 at the phase transformation temperature. Lattice con-stants of the grown crystlals were determined to be aR=5.3806 $\AA$ and $\alpha$=60.043$^{\circ}$ by the least square method.

• Journal of the Economic Geographical Society of Korea
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• v.1 no.1
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• pp.33-56
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• 1998

This study examines the characteristics of service economies and their impacts on the spatial transformation of Korea during the last IS years. This study reviews the different perspectives for the tertiarization Process. It focuses on the spatial variation in the growth and location of Producer service industries. Based on the analyses of industrial and occupational compositions, services. particularly producer services, have played a major role in creating new job opportunities since the late 1980s. The ratio of services to merchandise trade is approximately 1:4, but service trades have increased since the early 1990s. Producer service activities have grown very rapidly, and the information processing service has been over-concentrated in Seoul. Further headquarters of bank and insurance services are overwhelmingly concentrated into Seoul. The firms whose headquarters are located in Seoul have linkage Pattern on a nationwide scale. The pattern of employment growth in producer services shows a clear core-Periphery disparity. In the light of the observed pattern of regional differentiation in producer service employment, some wider implications of the distribution of producer service activities for regional economic Performance are considered.

• Journal of the Korean Home Economics Association
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• v.34 no.2
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• pp.43-55
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• 1996

The purpose of this study was to investigate the slacks pattern making on the movement-fitness of the knee region. The experimental items were divided into the lower limb movement (M1~M5) and slacks pattern designs (4 : basic pattern, in-pleats, side-pleats, seam-line increase). This study was done by clothing pressure test, sensory evaluation test and the difference shape-transformation of wearing-slacks. The summarized finding resulted from experiments and investigation are suggested as follows ; First, the clothing pressure test showed that the order of clothing pressure in the movement was the rabbit leap movement (M3), the sit on knees (M4), the nobleman sitting (M5), the sit on chair (M2) from the highest to the lowest. In the comparison of clothing pressure tested by blocks of lower-limb, center front knee region shows the highest of 300g/cm2. In it by constructional methods, the clothing pressure of in-pleats, side-pleats methods shows lower than basic pattern, hem-line increase methods. Also in comparison of the two methods, in-pleats method shows lower than side-pleats method. Second, by the sensory evaluation test based on the lower-limb movements and constructional methods of slacks, it was found that the functional factor score of the rabbit leap movement was also the waist, hip, knee region was the lowest in all blocks. And in the comparison of constructional methods, in-pleats method was the highest in all methods. Third, in consideration of the difference in the shape-transformation of wearing-slacks on the movement-fitness, pleats pattern design methods showed that the ratio of shape-transformation was lower than basic on seam-line increase methods. But the difference of the side-pleats and in-pleats methods was litle. According to these investigation, the slacks pattern making caused by movement-fitness on the knee region, in-pleats design method was the functional slacks pattern.

• Geophysics and Geophysical Exploration
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• v.19 no.2
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• pp.84-90
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• 2016

The validation of performance test for newly developed or old-used sensor is very important in the earthquake monitoring and seismology using earthquake data. Especially the frequency response of the sensor is mainly used to correct the earthquake data. The technique of the calculation of phase and amplitude with Hilbert transformation for earthquake data that is filtered with band limited frequency in time domain is applied to calculate the frequency response of the sensor. This technique was tested for the acceleration sensors, CMG-5T of 1g and 2g installed on the vibration table at the laboratory and we could obtain satisfactory result. Tohoku large earthquake in 2011 observed at the station SNU that has accelerometer, ES-T and seismometer, STS-2 operated by KIGAM was also used to test the field data applicability. We could successfully get the low frequency response of broad band sensor, STS-2. The technique by using band limited frequency filter and Hilbert transformation showed the superior frequency response to the frequency spectrum ratio method for noisy part in data.

• Korean Institute of Interior Design Journal
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• v.21 no.5
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• pp.280-288
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• 2012

The objective of this study was to analyze the characteristics of traditionality expressions at modernized Chinese restaurant in Hong Kong. As a case study, the study examined 12 modernized Chinese restaurants in Hong Kong. The gathered data were categorized and examined according to the ways of traditionality expressions, which included reproduction, transformation, and reinterpretation of traditional components. Each of the components was measured for the amount of traditional or modernity expression on a five-point scale. The five-point scoring system put an emphasis on tradition; 1 point was given to principal modernity(modernity: 90-100% + tradition: 0-10%), 2 points were given to principal modernity + auxiliary tradition(modernity: 70-90% + tradition: 10-30%), 3 points were given to the same ratio between tradition and modernity(modernity: 40-60% + tradition: 40-60%), 4 points were given to principal tradition + auxiliary modernity(modernity: 10-30% + tradition: 70-90%), and 5 points were given to principal tradition(modernity: 0-10% + tradition: 90-100%). The analysis performed according to those criteria and methodologies led to the following findings and conclusions: TM style, in which modernity was principal, usually did transformation and reinterpretation of traditionality. As for the design attributes of the styles, the TM style, they processed a majority of the spatial components as modern or reinterpretation of traditionality, which would be easily considered to be modern without careful observation, and applied a small amount of direct reproduction or transformation, which gives out a direct hint at traditionality, to attract more attention. Many of the spatial components did not express traditionality directly, expressing it indirectly or metaphorically. Traditionality was expressed in a small number of the spatial components, thus serving as a focus or impact point in the given space.