• Journal of the Korean GEO-environmental Society
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• v.21 no.9
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• pp.25-32
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• 2020

The underground utilities installed under the ground is an important civil engineering structure, such as water supply and sewerage pipes, underground power lines, various communication lines, and city gas pipes. Such underground utilities can be exposed to risk due to external factors such as concentrated rainfall and vehicle load, and it is important to select and construct an appropriate backfill material. Currently, a method mainly used is to fill the soil around the underground utilities and compact it. But it is difficult to compact the lower part of the buried pipe and the compaction efficiency decreases, reducing the stability of the underground utilities and causing various damages. In addition, there are disadvantages such as a decrease in ground strength due to disturbance of the ground, a complicated construction process, and construction costs increase because the construction period becomes longer, and civil complaints due to traffic restrictions. One way to solve this problem is to use a liquid filler. The liquid filler has advantages such as self-leveling ability, self-compaction, fluidity, artificial strength control, and low strength that can be re-excavated for maintenance. In this study, uniaxial compression strength test and fluidity test were performed to characterize the mixed soil using marine clay, stabilizer, and in-situ soil as backfill material. A freezing-thawing test was performed to understand the strength characteristics of the liquid filler by freezing, and in order to examine the effect of the filling materials on the corrosion of the underground pipe, an electrical resistivity test and a pH test were performed.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.03a
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• pp.79-88
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• 2008

Since the hydraulic fracturing field testing method was introduced first to Korean geotechnical engineers in 1994, there have been lots of progresses in a hardware system as well as an interpretation tool. The hydrofracturing system of first generation was the pipe-line type, so it was not easy to handle. It had been modified to a wire-line system at their second generation. It was more compact one but it also needed an additional air-compressor. Our current system is much more compact and operated by all-in-one system, so it doesn't need an additional air-compressor. With a progress in a hardware system, the software for analyzing the in-situ stress regime has also been progressed. For example, the shut-in pressure, which is the most ambiguous parameter to be obtained from hydrofracturing pressure curves, can now be acquired automatically from the various methods. While the hardware and software for hydrofracturing tests are being developed during the last decade, the author could accumulate the field test results which can cover the almost whole area of South Korea. Currently these field data are used widely in a feasibility study or a preliminary design step for tunnel construction in Korea. Regarding the difficulties in a site selection and a test performance for the in-situ stress measurement at an off-shore area, the in-situ stress regime obtained from the field experiences in the land area can be used indirectly for the design of a sub-sea tunnel. From the hydrofracturing stress measurements, the trend of magnitude and direction of in-situ stress field was shown identically with the geological information in Korea.

• The Journal of Korean Medical History
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• v.15 no.1
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• pp.63-146
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• 2002

Huh-Im(許任, 1570~1647) was an acupuncture doctor of Chosun(朝鮮) era through the late 16th century and early 17th century. Even though he was a person of low birth, he participated in the loyal medication through three loyal generations, Sunjo(宣祖), Kwanghaegun(光海君) and Injo(仁祖). He was recognized of his services and became an official, 'Dangsanggwan'(堂上官) and Kyunggi(京畿) district official several times. In the early Chosun era, acupuncture medicine was focused. During the late 16th century, Imjin(壬辰) war aroused more needs about acupuncture medicine, and acupuncture doctors showed remarkable work. Under these circumstances, Huh-Im(許任)'s fame spread throughout the country. Huh-Im(許任) wrote ChimGuKyungHumBang("鍼灸經驗方") in 1644 based on his lifetime clinical acupuncture & moxibustion experience. It was the first specialized book of acupuncture in Chosun era. This event took place 30 years after DongEuiBoGam - Acupuncture Chapter("東醫寶鑑-鍼灸篇") was published. But it was not influenced much by DongEuiBoGam - Acupuncture Chapter("東醫寶 鑑-鍼灸篇") in the form or contents. ChimGuKyungHumBang("鍼灸經驗方") and Huh-Jun(許浚)'s DongEuiBo- Gam - Acupuncture Chapter("東醫寶鑑-鍼灸篇") were the fruits of the middle Chosun, and they are complementary to each other in theory and practice. The chief distinctions of ChimGuKyungHumBang("鍼灸經驗方") are in it's compact and practical edition and a lot of his clinical acupuncture prescriptions mentioned in the book. Huh-Im(許任) not only accepted the existing books such as NaeKyung("內經"), DongInSuHyulChimGuDoKyung and Shin- Eung Kyung("神應經") with his point of view and clinical experience, but also showed creative operation of studies. Indicating incorrect acupuncture points(訛穴), acupuncture remedy based on the visceral pathogenesis(臟腑病機) and the channel pathogenesis, research on new acupuncture points, sorting out plenty of outer meridian acupuncture points(經外奇穴), creating supplementary and purging acupuncture method(鍼補瀉法) which is a change of hand treatment of KiHyoYangBang("奇效良方"), operating variety of acupuncture and moxibustion treatments, and application of acupuncture treatments on surgery field such as intumescences and emergency cases are the examples. Huh-Im(許任)'s ChimGuKyungHumBang("鍼灸經驗方") influenced on the folk remedy books(民間經驗方書) in the late Chosun era. Compact and practical characteristics of the book let acupuncture treatment be freindly to the people. It can be confirmed in JeungBoSanRimKyungJe-Emergency Chapter("增補山林經濟-救急篇") or the formation of SaAmChimBob(舍巖鍼法). ChimGuKyungHumBang("鍼灸經驗方") was introduced to Japan in 18th century and published twice. ChimGuJibSung("鍼灸集成"), known as an acupuncture medical book of late Qing dynasty(淸末, 1874), is confirmed to be an plagiarization of DongEuiBoGam-Acupuncture Chapter("東醫寶鑑-鍼灸篇") and ChimGuKyungHum- Bang("鍼灸經驗方") of 17th century Chosun. Confusions and errors arouse from mistaken editional trend of ChimGuJIbSung("鍼灸集成") which had not disclosed it's original author and the title of the book must be reformed. In this way, fruits of acupuncture of the middle Chosun era including Huh-Im(許任)'s ChimGuKyungHumBang("鍼灸經驗方") will take a right place in acupuncture medicine history.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.359-370
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• 2000

The purpose of this investigation was to observe the viscoelastic properties of five commercial flowable(Aeliteflo, Flow it, Revolution, Tetric flow, Compoglass flow), three conventional hybrid(Z-100, Z-250, P-60) and two condensable(Synergy compact, SureFil) resin composites. A dynamic oscillatory shear test was done to evaluate the storage shear modulus (G'), loss shear modulus(G"), loss tangent(tan ${\delta}$) and complex viscosity(${\eta}^*$) of the resin composites as a function of frequency - dynamic frequency sweep test from 0.01 to 100 rad/s at $25^{\circ}C$ - by using Advanced Rheometric Expansion System(ARES). To investigate the effect on the viscosity of resin composites of filler volume fraction, the filler weight % and volume % were measured by means of Archimedes' principle using a pyknometer. The results were as follows 1. The complex viscosity ${\eta}^*$ of flowable resins was lower than that of hybrid resins and significant differences were observed between brands. The complex viscosity ${\eta}^*$ of condensable resins was higher than that of hybrid resins. The order of complex viscosity ${\eta}^*$ at ${\omega}$=10 rad/s was as follows, Surefil, Synergy compact, P-60, Z-250, Z-100, Aeliteflo, Tetric flow, Compoglass flow, Flow it, Revolution. The relative complex viscosity of flowable resins compared to Z-100 was 0.04~0.56 but Surefil was 30.4 times higher than that of Z-100. 2. The storage shear modulus G' and the loss shear modulus G" of flowable resins were lower than those of hybrid resins but those of condensable resins were higher. The patterns of the change of loss tangent, tan ${\delta}$, of resin composites with increasing frequency were significantly different between brands. The phase angles, ${\delta}$, ranged from $30.2{\sim}78.1^{\circ}$ at ${\omega}$=10 rad/s. 3. All composite resins represent pseudoplastic nature with increasing shear rate. 4. The complex shear modulus $G^*$ and the phase angle ${\delta}$ was represented by the frequency domain phasor form, $G^*({\omega})=G^*e^{i{\delta}}=G^*{\angle}{\delta}$. The locus of frequency domain phasor plots in a complex plane was a valuable method that represent the viscoelastic properties of composite resins. 5. There was no direct linear correlationship but a weak positive relation was observed between filler volume % or weight % and the viscosity of the resin composites.

• Korean Journal of Optics and Photonics
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• v.19 no.5
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• pp.349-359
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• 2008

For an inner-focusing 3-groups zoom lens system, this study suggests a new initial design method which applies the process that changes thin lenses into thick ones effectively and quickly, using the hybrid lens system(thin lens+thick lens). In other words, the hybrid lens system is the semi-automatic design process that makes the thin lens of one group change into a thick one while the other groups are composed of thin lenses. Keeping the total power of the system fixed, the power of each group and the distance between principal planes can be fixed. Of course, the other groups composed of thin lenses could be changed into thick lenses sequentially by this process. This design conception results in the 1/4" 5 M inner-focusing 3-groups 2x zoom lens system satisfying the specifications and performances of zoom lens for phone cameras. Also aspherization on lens elements of glass and plastic material enhanced the resolution and reduced the lens size. As a result, we have an ultra-compact inner-focusing 3-groups 2x zoom lens system for a phone camera, with a slim size with TTL of 9.8 mm.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.319-328
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• 2003

The purpose of this paper is to develop a medical laser system using the semiconductor diode laser in order to photodynamic cancel therapy as a light source. The ideal light source for photodynamic therapy would be a homogeneous nondiverging light with variable spot size and specific wavelength with stability. After due consideration in this point, in this paper, we used a diode laser resonator of 635nm wavelength. The development laser system have a statistical laser out beam with accuracy control using the constant current control of method and clinic-friendly with compact. In order to protect the diode resonator from the over-current, the rush-current and electrical fault, we specially designed. The most importance therapeutic factor are the radiation mode for cancer therapy. So we developed the radiation mode of CW(Continuous Wave), long pulse, short pulse, and burst pulse and can adjust the exposure time from several milli-second to several minute. The experimental result shows that laser beam power was increased linear from 10mW to 300mW according to the increasing input current and the increasing exposure time. The developed new compact diode laser system have a stability of output power and specific wavelength with easy control and transportable for many applications of PDT.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.291-304
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• 2021

Updating a forest type map is essential for sustainable forest resource management and monitoring to cope with climate change and various environmental problems. According to the necessity of efficient and wide-area forestry remote sensing, CAS500-4 (Compact Advanced Satellite 500-4; The agriculture and forestry satellite) project has been confirmed and scheduled for launch in 2023. Before launching and utilizing CAS500-4, this study aimed to pre-evaluation the possibility of satellite-based tree species classification using RapidEye, which has similar specifications to the CAS500-4. In this study, the study area was the Chuncheon forest management complex, Gangwon-do. The spectral information was extracted from the growing season image. And the GLCM texture information was derived from the growing and non-growing seasons NIR bands. Both information were used to classification with random forest machine learning method. In this study, tree species were classified into nine classes to the coniferous tree (Korean red pine, Korean pine, Japanese larch), broad-leaved trees (Mongolian oak, Oriental cork oak, East Asian white birch, Korean Castanea, and other broad-leaved trees), and mixed forest. Finally, the classification accuracy was calculated by comparing the forest type map and classification results. As a result, the accuracy was 39.41% when only spectral information was used and 69.29% when both spectral information and texture information was used. For future study, the applicability of the CAS500-4 will be improved by substituting additional variables that more effectively reflect vegetation's ecological characteristics.

• Korean Journal of Remote Sensing
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• v.38 no.3
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• pp.311-326
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• 2022

The Compact Advanced Satellite 500-4 (CAS500-4) is under development to efficiently manage and monitor forests in Korea and is scheduled to launch in 2025. The National Institute of Forest Science is developing 36 types of forestry applications to utilize the CAS500-4 efficiently. The products derived using the remote sensing method require validation with ground reference data, and the quality monitoring results for the products must be continuously reported. Due to it being the first time developing the national forestry satellite, there is no official calibration and validation site for forestry products in Korea. Accordingly, the author designed a calibration and validation site for the forestry products following international standards. In addition, to install calibration and validation sites nationwide, the authors selected appropriate sensors and evaluated the applicability of the sensors. As a result, the difference between the ground observation data and the Sentinel-2 image was observed to be within ±5%, confirming that the sensor could be used for nationwide expansion.

• Composites Research
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• v.19 no.1
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• pp.29-35
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• 2006

The avoidance of enemy's radar detection is very important issue in the modem electronic weapon system. Researchers have studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), 'C'-type shell and 'U'-type shell, were fabricated using fiber-reinforced composite materials and their radar cross section (RCS) were evaluated. The absorption layer was composed of glass fiber reinforced epoxy and nano size carbon-black, and the reflection layer was fabricated with carbon fiber reinforced epoxy. During their manufacturing process, undesired thermal deformation (so called spring-back) was observed. In order to reduce spring-back, the bending angle of mold was controlled by a series of experiments. The spring-back of parts fabricated by using compensated mold was predicted by finite element analysis (ANSYS). The RCS of RAS shells were measured by compact range and predicted by physical optics method. The measured RCS data was well matched with the predicted data.

• Journal of the Korean Association of Geographic Information Studies
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• v.27 no.3
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• pp.14-29
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• 2024

As a part of domestic and international 'Time-Urban Planning,' the concept of 'n-minute city' is being discussed. However, relevant research in this area remains insufficient. Particularly in South Korea, studies focusing on n-minute cities based on accessibility are notably lacking. Therefore, this study aims to investigate Changwon City, dividing it into urban and non-urban areas. For each of the eight different aspects of 'Living SOC', we analyze accessibility and propose fundamental directions for creating n-minute cities in Changwon. The data are collected at a 100×100m cell level, including population and the location of SOC facilities. The road network data are also constructed, and the network analysis method of QGIS employed to measure accessibility to each facility. The results indicate that in urban areas, the average travel time to Living SOC is approximately 12 minutes. However, even within urban areas, locations on the outskirts take around 16 minutes, showing some variation compared to the city center. Non-urban areas have an average travel time of about 18 minutes, indicating poor accessibility. Additionally, there is significant variability in travel time to facilities depending on the specific cell in non-urban areas, necessitating targeted solutions. Considering the ongoing population decline in South Korea, achieving n-minute cities requires not only reconsidering customized facility supply and placement based on regional characteristics but also fundamentally restructuring urban spaces through strategies such as compact cities to optimize land use.