• Journal of the Korean Wood Science and Technology
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• 제9권3호
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• pp.1-6
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• 1981

This study examined the radial variations in element demensions of mongolian oak (Quercus mongolica.), elm (Ulmus japonica.), maackia(Maackia amurensis.), castor aralia (Kalopanax pictus.) from pith outwards. Disks were cut from the d.b.h.(above 1.2m) of each species and specimen for tangential pore diameters, fiber length, ray height and width were taken from 1-3rd, 5th, 10th, 15th.............40th ring number from pith. The tangential pore diameters in the earlywood increased rapidly near the pith and then maintained almost constant or very gradually increased diameters in about 20th-30th ring number from pith. In the latewood, tangential pore diameters gradually increased from pith to outwards though the increment is smaller than in early wood. Radial variations of ray height and width maintained almost constant, gradually increased or rapidly increased diameters and then maintained almost constant from pith to outwards. Patterns of radial variations in the fiber length were almost coincident with patterns of earlywood pore diameters, and of ray height or width in Ulmus japonica and Maackia amurensis.

• Journal of architectural history
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• 제12권3호
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• pp.53-63
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• 2003

Tree-ring chronologies can be used to date historical buildings by matching them with the chronologies of living trees or previously dated samples. Tree-ring dating gives a calendar year to each tree ring and produces the felling dates of logs or woods which had been used for buildings. In Korea, several chronologies of Japanese red pine(Pinus densiflora Sieb. et Zucc., 'sonamu' in Korean), a major species for the wooden building materials, have been developed and used for dating historical buildings. In this study, Tongmyungjeon Hall of Changkyung Palace in Seoul was dated by tree rings. The present Tongmyungjeon Hall was known to be reconstructed in A.D. 1834 after burned-out in A.D. 1790. We sampled total of 122 wood samples which were replaced during the repair process in 2002-2003. Felling dates of the samples were determined by the dendrochronological crossdating method. Crossdating method employs graphic comparison of the master patterns (ring-width chronologies of known dates) with those of the sample chronologies of unknown dates. Tree-ring dates confirmed that the reconstruction of 1834 utilized second-handed timbers as well as fresh-cut ones. The felling dates of wooden floor frames were mostly A.D. 1913, indicating the 'Ondol' floors were changed to the wooden floors around 1914 when the Japanese rulers brutally destroyed the royal Korean Palaces and transformed palace buildings to their offices or exhibition halls after occupying Korea in 1910. This study proved that tree-ring dating was a useful and accurate method to identify the critical dates for the history of Korean traditional buildings.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.613-617
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• 2001

The test items like as endurance, air leakage and oil endurance test is requested for reliability evaluation about O-ring which is a kind of core machinery accessories of semi-conduct manufacturing equipment. For verification of these, we design and manufactured a test system for endurance, air leakage and oil endurance of O-ring for semi-conduct manufacturing equipment, and also performed the test for two kinds of O-ring, as it were Viton and Kalretz. The characteristics of this test equipment consist in realization of the test conditions of semi-conduct manufacturing equipment and satisfying the test method. The test conditions are cut gas, vacuum grade, temperature and revolution numbers in the endurance test system, vacuum grade and temperature in the air leakage test system, temperature and time in the oil endurance test system. The separating test results for wearing which is an oil endurance test item, the wearing index of domestic produced Viton O-ring is higher than foreign product by 2%, wearing rate of Kalretz O-ring better than Viton O-ring by 17%, and particles existed in various place. The test result of air leakage which is measured through the RGA sensor used Helium, the vacuum grade was $10^-3$Torr. And the test result of oil endurance, the volume change rate was 7~15%. Hereafter, we intend to analysis the reliability test evaluation and to utilize for domestic manufacturing companies by establishing data base and developing reliability softwares.

• Journal of Korean Tunnelling and Underground Space Association
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• 제20권1호
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• pp.183-195
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• 2018

Recently, the need for research on vertical shaft excavation is increasing with the increase of the demands for the underground and utility tunnels. As a part of the R&D project of the Ministry of Land, Infrastructure and Transport, CUT (center for utility tunnel) has developed "Ring cut method". "Ring cut method" is a method to improve the stability of the ground against the basal heave by excavator wall pre-penetration during vertical shaft excavation. In this study, the basal heave was simulated by centrifugal model test. The basal heave, ground subsidence, and ground deformation of surrounding ground were analyzed by soil plug effect from wall pre-penetration. It was found that the soil plug could control the basal heaving and ground subsidence, and verified that the 'Ring cut method' could be a good countermeasure for the ground stability against the basal heave.

• Journal of architectural history
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• 제15권2호
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• pp.23-38
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• 2006

During the repair and restoration of the Daewoongjeon Hall of Youngguksa Temple, species identification and tree-ring dating for both present wood elements and charred ones excavated under the Hall, were conducted. The species of 74 wood elements of Daewoongjeon Hall, were identified as Pinus densiflora Sieb. et Zucc. and only 1 was identified as exotic Pinus species. The latter wood, which was used in the laths, seems to have been replaced during past repairs. Many documentary records and various artifacts pertaining to Youngguksa Temple are being excavated, but none described precisely the construction date of the present Daewoongjeon Hall. Also, from beneath the Daewoongjeon Hall, cornerstone and foundation of previous building and several charred wood elements were excavated. In comparing the direction of the stone columns of foundation of the previous structure and the existing Daewoongjeon Hall, the previous structure was rotated in an angle of approximately $15^{\circ}$. Therefore, in order to find the association of the previous structure with the present Daewoongjeon Hall, tree-ring dating was conducted. The dating of 41 original timbers and 14 roof-filling timbers of the present construction elements revealed that the last annual ring was of A. D. 1703 with complete latewood, indicating that those woods was cut some time between the autumn of 1703 and spring of 1704, and the building was erected in 1704 when we assume no period of wood storage. The year of the last annual ring of the charred elements, which were excavated from beneath the Daewoongjeon Hall, was analyzed as 1674. The cutting year of the woods used for the present building began in 1698, therefore, it can be presumed that the Daewoongjeon Hall before the fire was a structure that was elected shortly after 1674 and that a catastrophic fire occurred some time between 1674 and 1698.

• Journal of the Korean Wood Science and Technology
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• 제45권1호
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• pp.85-95
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• 2017

This study aimed at more precisely estimating the age of big old trees using dendrochronological method. Gesan-gun in Chungbuk (CBGS), Gurye-gun in Jeonnam (JNGR) and Uljin-gun in Gyeongbuk (GBUJ) were study areas and Zelkova serrata (ZS) and Pinus densiflora (PD) selected as protected trees therein were used as experimental tree species. The increment cores were extracted from 12, 8, and 6 ZSs and 10, 3, and 9 PDs in CBGS, JNGR, and GBUJ, respectively, using an increment borer (${\phi}5.2mm$). In order to clearly distinguish tree-ring boundary, the surface in the transverse section was cut for ZS using a sliding microtome and sanded for PD using a sand paper. Ring widths were measured in the resolution of 0.01 mm. Based on the measurement values, 203-year long (1813-2015) ZS local master tree-ring chronologies were successfully established and 175-year long (1841-2015) ZS local master tree-ring chronology for JNGR was also successfully established. In the case of PD, 154-, 175-, and 250-year long local master tree-ring chronologies for CBGS, JNGR, and GBUJ were successfully established, respectively. In the comparisons between local master tree-ring chronologies, they showed low t-values and Glks. According to the comparisons of the local master tree-ring chronologies with 50-year (1950~2000) average temperature and precipitation distribution maps, the annual variations of local master tree-ring chronologies seem to be determined by not temperature but precipitation. For such cross-dating therefore more local master tree-ring chronologies have to be established at the least based on the distribution map for precipitation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제14권6호
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• pp.262-266
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• 2004

Rutile single crystals were grown by the skull melting method. Ti metal ring was used for initial RF induction heating. The grown crystals were cut into wafer of 5.5 mm diameter and 1mm thickness. The wafers were annealed in air at $1300^{\circ}C$ up to 15 hours and their transmittance spectra $(\lambda= 200~25000 nm)$ were obtained.

• Textile Coloration and Finishing
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• 제14권1호
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• pp.58-65
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• 2002

This study surveys the physical properties of Solo-spun fabrics related to the characteristics of Solo-spun yarns, which were described in previous reports. For this purposes, 6 kinds of fabrics were woven on the pilot loom. 3 kinds of Solo-spun yarns with the 3 level of twist mutiplier of Nm 1/30 and 3 kinds of conventional ring-spun yarns with the same levels of twist multipliers of the same yarn counts. The fabrics were of 2/2 twill and clear-cut finished. The physical properties were surveyed by means of KES-FB system. Solo-spun fabrics seemed to be stiffer than ring spun fabrics as showing the lower extensibility with higher tensile energy, the higher bending rigidity, and the higher shear rigidity. Solo-spun fabrics showed the lower value in surface friction coefficient and surface roughness. For fabric abrasion tests, Solo-spun fabrics showed the higher pill resistance.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제59권5호
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• pp.1005-1009
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• 2010

This paper presents a digitally-controlled filter calibration technique for biquad RC filter using self oscillation. The biquad RC filter is converted to a fully-differential ring oscillator by changing its resistor connections, where the oscillation frequency reflects the cut-off frequency. The proposed calibration circuit measures the oscillation frequency by counting with a fixed higher-frequency clock and then tunes it to a desired frequency with a digital frequency-locked loop including a PI controller. Because the proposed circuit directly measures the cut-off frequency of the filter itself and calibrates it with the small area digital circuits, the area and the power consumption are much small compared with conventional works. When it is implemented in a 65nm CMOS process, the calibration circuit except the filter consumes the area of 80um X 50um and power consumption is 443uA at 1.2 V supply voltage.

• Journal of the Korea institute for structural maintenance and inspection
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• 제5권3호
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• pp.225-231
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• 2001

When building tunnels beneath riverbeds where very large quantities of groundwater inflow exist, added to high water head the soil supporting conditions are very poor because the soil consists of sand and silt, etc. It is necessary to have grouting and mini pipe roof installed in the region for ground reinforcement to decrease permeability. According to this result of horizontal boring and laboratory soil testing, ground reinforcement was achieved by L.W grouting for range of 3.0 times the tunnel radius, to increase stability of the tunnel we used the ling-cut method, 0.8m for one step excavation, shotcrete with 25cm thick, steel lib with H-$125{\times}125$. and a temporary shotcrete invert 20cm thick was installed to prevent deformation of the tunnel.